Liner-type, antistatic topcoat system for aircraft canopies and windshields

ABSTRACT

A coated substrate includes: a substrate; an electrically conductive multilayer stack on the substrate; and a coating on the electrically conductive multilayer stack. A thickness of the coating is 5 to 10 mils and the coating includes a conductive, anti-static tiecoat on the electrically conductive multilayer stack; and a conductive, anti-static topcoat on the conductive, anti-static tiecoat. The conductive, anti-static tiecoat and the conductive, anti-static topcoat are formed from a coating composition including a hydrophobic first aliphatic polyisocyanate, a second aliphatic polyisocyanate including a hydrophilic portion, a polyester polyol, a hydrophilic polyol, and a fluorinated polyol compound is disclosed.

STATEMENT REGARDING POTENTIAL NATIONAL SECURITY CONCERN

This application contains subject matter that may be controlled under USInternational Traffic in Arms Regulations (“ITAR”), 22 CFR Para.120-130. Therefore, this application should be considered by theappropriate federal agency for imposition of a secrecy order.

BACKGROUND

Polyurethane polymers can be used as a coating for a variety ofapplications. For example, they can be used as a coating for coatedsubstrates, such as a coated transparency for an aircraft. Aircrafttransparencies (e.g., canopies), and particularly stealth aircraftcanopies, preferably include a low resistance (i.e., high electricalconductivity) layer (or layers) to prevent or reduce the buildup ofstatic charge and to provide radar attenuation. Static charge canbuildup on a canopy as the result of precipitation static and/orlightning strikes, and may interfere with various functions of theaircraft. By including a low resistance layer (or layers), an aircraftcanopy can drain or dissipate static electricity and thereby prevent orreduce the buildup of static charge on the canopy. The low resistancelayer (or layers) may be coated with a high resistance coating (e.g., apolyurethane antistatic topcoat), as long as static charge can betransferred through the organic topcoat into the low resistance layer(or layers).

Modern jet aircraft canopies, such as F-22 stealth fighter canopies, aretypically made of polymeric materials. Such materials are desirablebecause of their light weight, high strength, and ease of shaping. Mostpolymeric materials, however, do not meet the requirements for stealthaircraft, such as low sheet resistance and the ability to withstandextreme weather conditions. As a result, coatings (e.g., organic andinorganic coatings) are employed to impart high electrical conductivityand other characteristics to the canopy.

SUMMARY

A coated substrate includes: a substrate; an electrically conductivemultilayer stack on the substrate; and a coating on the electricallyconductive multilayer stack, a thickness of the coating being 5 to 10mils and the coating including: a conductive, anti-static tiecoat on theelectrically conductive multilayer stack; and a conductive, anti-statictopcoat on the conductive, anti-static tiecoat, a thickness of thecoating being 5 to 10 mils, and the conductive, anti-static tiecoatbeing formed from a coating composition including a hydrophobic firstaliphatic polyisocyanate, a second aliphatic polyisocyanate including ahydrophilic portion, a polyester polyol, a hydrophilic polyol, and afluorinated polyol.

A thickness of each of the conductive, anti-static topcoat and theconductive, anti-static tiecoat may be 2.5 to 5 mils.

The thickness of the coating may be 5 to 8 mils.

A thickness of each of the conductive, anti-static topcoat and theconductive, anti-static tiecoat may be 2.5 to 4 mils.

The thickness of the coating may be 6 to 8 mils.

A thickness of each of the conductive, anti-static topcoat and theconductive, anti-static tiecoat may be 3 to 4 mils.

A thickness of the conductive, anti-static tiecoat may be at least 3mils.

A thickness of the conductive, anti-static topcoat may be at least 3mils.

The conductive, anti-static tiecoat may be substantially free ofinherently conductive polymers, ionic liquids, conductive oxides andcarbon nanotubes.

The conductive, anti-static topcoat may be substantially free ofinherently conductive polymers, ionic liquids, conductive oxides andcarbon nanotubes.

The coated substrate may further include a tiecoat between the substrateand the electrically conductive multilayer stack.

The coated substrate may further include a basecoat between the tiecoatand the electrically conductive multilayer stack.

The coated substrate may further include a primer layer between theelectrically conductive multilayer stack and the conductive, anti-statictiecoat.

The coating may have a resilience such that the coating can be stretchedto a length 50% or more longer than the as-formed length of the coatingsubstantially without tearing the coating.

The coating may have a resilience such that the coating can be stretchedto a length 100% or more longer than the as-formed length of the coatingsubstantially without tearing the coating.

The coating may have a resilience such that the coating can be stretchedto a length 200% or more longer than the as-formed length of the coatingsubstantially without tearing the coating.

The second aliphatic polyisocyanate may further include a hydrophobicportion.

The hydrophobic portion of the second aliphatic polyisocyanate mayinclude an isophorone diisocyanate moiety or a derivative thereof.

The hydrophilic portion of the second aliphatic polyisocyanate mayinclude a polyether chain.

The second aliphatic polyisocyanate may include a polyether chain bondedto an isophorone diisocyanate trimer.

The hydrophobic first aliphatic polyisocyanate may have an isocyanatefunctionality in a range of 3.0 to 4.2.

The hydrophobic first aliphatic polyisocyanate may be selected from thegroup consisting of biuret-based polyisocyanates, isocyanuratering-based polyisocyanates, and combinations thereof.

A weight ratio of the hydrophobic first aliphatic polyisocyanate to thesecond aliphatic polyisocyanate may be in a range of about 95:5 to about85:15.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of embodiments of the present disclosure willbe better understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings, in which:

FIG. 1 is an exploded, cross-sectional view of an embodiment of a coatedsubstrate including a conductive, anti-static tiecoat and a conductive,anti-static topcoat;

FIG. 2 is an exploded, cross-sectional view of a coated substrateaccording to an embodiment of the present disclosure;

FIG. 3 is an exploded, cross-sectional view of a portion of anelectrically conductive multilayer stack according to an embodiment ofthe present disclosure;

FIG. 4 is an exploded, cross-sectional view of another portion of anelectrically conductive multilayer stack according to an embodiment ofthe present disclosure;

FIG. 5 is an exploded, cross-sectional view of an electricallyconductive multilayer stack according to an embodiment of the presentdisclosure;

FIG. 6 is an exploded, cross-sectional view of a coated substrateaccording to another embodiment of the present disclosure;

FIG. 7 is an exploded, cross-sectional view of a coated substrateaccording to another embodiment of the present disclosure; and

FIG. 8 is an exploded, cross-sectional view of a coated substrateaccording to another embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following description and in the claims, various layers aredescribed as being “on,” “over,” or “positioned over” one or moreadditional layers. This language simply denotes the relative positionsof the layers. Thus, in some embodiments, two layers are literally rightnext to each other, while in other embodiments, the same two layers areseparated by one or more additional layer(s). In each case, one of thetwo layers is considered to be “on,” “over,” or positioned over” theother layer. Also, “on” or “over” can mean “below.” For example, a layerthat is “on” or “over” another layer can also be considered “below” theother layer, depending upon the point of view.

As used herein, the term “coated substrate” or “coated transparency”refers to a substrate or transparency that has been protected (e.g.,coated) with one or more layer(s) on the substrate. The substrate ortransparency can be made of glass or plastic, coated or uncoated, andcan form a window or a windshield of a car, aircraft, boat, building, orany other suitable vehicle or structure.

Aspects of embodiments of the present disclosure are directed toward acoating that is tough, durable and weather resistant, yet is stillpliable and flexible. FIG. 1 is a cross-sectional view showing anembodiment of a coated substrate 100 including a substrate 10, anelectrically conductive multilayer stack 120 on the substrate, and acoating 103 on the electrically conductive multilayer stack. The coatingincludes a conductive, anti-static tiecoat 107 on the electricallyconductive multilayer stack, and a conductive, anti-static topcoat 105on the conductive, anti-static tiecoat. In some embodiments, a thicknessof the coating (e.g., a total thickness of the conductive, anti-statictiecoat and the conductive, anti-static topcoat) is 5 to 10 mils (127 to254 μm). The coating may be a liner kind of coating. As used herein, thestatement “liner kind of coating” refers to a coating having a thicknessof at least 5 mils (e.g., a thickness of 5 to 10 mils) and a resiliencesuch that the coating can be stretched to a length 50% or more longerthan the as-formed length (the initial, unstretched length) of thecoating substantially without breaking (e.g., substantially withouttearing or cracking or without tearing or separating into two separateportions). In some embodiments, the coating can be stretched to a length100% or more (e.g., 100% to 300%) longer than the as-formed length (theinitial, unstretched length) of the coating substantially withoutbreaking (e.g., substantially without tearing or cracking or withouttearing or separating into two separate portions). In some embodiments,the coating can be stretched to a length 200% or more (e.g., 200% to300%) longer than the as-formed length (the initial, unstretched length)of the coating substantially without breaking (e.g., substantiallywithout tearing or cracking or without tearing or separating into twoseparate portions).

Embodiments of the conductive, anti-static tiecoat include apolyurethane and are highly resilient. The conductive, anti-statictiecoat functions as a shock absorber for impacts (e.g., high energyimpacts) of rain droplets in a rain erosion test. Rain erosionresistance properties of embodiments of the coated substrate includingthe conductive, anti-static tiecoat are significantly enhanced ascompared to coated substrates that do not include the conductive,anti-static tiecoat, but are otherwise the same. For example, a coatedsubstrate that includes the substrate (e.g., an acrylic substrate), theelectrically conductive multilayer stack on the substrate, and theconductive, anti-static topcoat on the electrically conductivemultilayer stack, but does not include the conductive, anti-statictiecoat, shows significantly compromised performance in a rain erosiontest at 550 mph and 575 mph. Further, a coating including a conductive,anti-static topcoat prepared utilizing a single flow coating does nothave suitable rain erosion resistance (e.g., does not pass the rainerosion test at 550 mph and 575 mph) and/or cosmetics. As used herein,the term “single flow” refers to a coating formed utilizing a singleapplication and curing of the coating. For example, a coating includingthe conductive, anti-static topcoat, but not the conductive, anti-statictiecoat, has not been prepared to be very thick (e.g., thicker than 5 or6 mils), cosmetically acceptable conductive, and/or to have suitablerain erosion resistance utilizing a single flow coating due to the highviscosities of the coating composition for forming the conductive,anti-static topcoat. The coated substrate of embodiments of the presentdisclosure (e.g., the coating including the conductive, anti-statictiecoat and the conductive, anti-static topcoat) provides significantlyimproved rain erosion resistance properties as compared to coatedsubstrates that include the conductive, anti-static topcoat, but do notinclude the conductive, anti-static tiecoat.

Embodiments of the coated substrate provide suitable rain erosionresistance (e.g., the coated substrate passes the rain erosion test at550 mph and 575 mph) by way of a relatively thick and resilientconductive, anti-static tiecoat. By including both the conductive,anti-static tiecoat and the conductive, anti-static topcoat, the coatingcan be made to be at least 5 mils thick and to have a resilience suchthat the coating can be stretched to a length 50% or more longer thanthe as-formed length (the initial, unstretched length) of the coatingsubstantially without breaking (e.g., substantially without tearing orcracking or without tearing or separating into two separate portions),and in some embodiments, the coating can be stretched to a length 100%or more (e.g., 100% to 300%) longer than the as-formed length (theinitial, unstretched length) of the coating substantially withoutbreaking (e.g., substantially without tearing or cracking or withouttearing or separating into two separate portions). In some embodiments,the coating can be stretched to a length 200% or more (e.g., 200% to300%) longer than the as-formed length (the initial, unstretched length)of the coating substantially without breaking (e.g., substantiallywithout tearing or cracking or without tearing or separating into twoseparate portions). While the present disclosure is not limited by anyparticular mechanism or theory, it is believed that due to theresilience of embodiments of the coating including the conductive,anti-static tiecoat, prolonged exposure in QUV and humidity tests do notsignificantly degrade the adhesion and rain erosion resistanceproperties of the coated substrate.

The total thickness of the conductive, anti-static topcoat and theconductive, anti-static tiecoat together (the combined thickness of theconductive, anti-static topcoat and the conductive, anti-static tiecoat)may be at least 5 mils (127 μm), for example, 5 to 10 mils (127 to 254μm), 6 to 10 mils (152.4 to 254 μm), 5 to 8 mils (127 to 203.2 μm), 5 to7 mils (127 to 177.8 μm), or 6 to 8 mils (152.4 to 203.2 μm). When thecoating has a thickness of at least 5 mils (the combined thickness ofthe conductive, anti-static topcoat and the conductive, anti-statictiecoat is at least 5 mils) the coating is expected to exhibitliner-type properties (or liner kind of properties) and good rainerosion performance at 575 mph. The conductive, anti-static topcoat andthe conductive, anti-static tiecoat may each have a thickness of 2.5 to5 mils (63.5 to 127 μm), 2.5 to 4 mils (63.5 to 101.6 μm), or 3 to 4mils (76.2 to 101.6 μm). In some embodiments, the conductive,anti-static topcoat and the conductive, anti-static tiecoat each have athickness of 2.56 to 2.76 mils (65 to 70 μm). In other embodiments, theconductive, anti-static topcoat and the conductive, anti-static tiecoateach have a thickness of at least 3 mils (e.g., at least 3 mils to 5mils). In still other embodiments, the conductive, anti-static topcoatand the conductive, anti-static tiecoat each have a thickness of 4 mils(101.6 μm) to have a combined thickness of 8 mils (203.2 μm).

Embodiments of the conductive, anti-static tiecoat are thick, resilient,and enhance the performance of the coated substrate in the rain erosiontest at 575 mph. When the coated substrate includes the thick (e.g., atleast 5 mils) and resilient conductive, anti-static tiecoat and a thickand resilient conductive, anti-static topcoat on the electricallyconductive multilayer stack on the substrate (e.g., a stretched acrylicsubstrate), the coated substrate exhibits good Bayer abrasion, QUV,steam, humidity, rain erosion, acid rain, salt-fog, and chemical/solventtest results along with good p-static charge dissipation capabilities.Embodiments of the conductive, anti-static tiecoat and the conductive,anti-static topcoat also have anti-static properties that allow thepassage of static charge through the conductive, anti-static tiecoatand/or the conductive, anti-static topcoat to the electricallyconductive multilayer stack for dissipation. For example, dissipation ofp-static charge may be performed primarily by the electricallyconductive multilayer stack (e.g., by a metal layer of the electricallyconductive multilayer stack). According to embodiments of the presentdisclosure, p-static charge (or other electric charge) passes throughthe conductive, anti-static topcoat and the conductive, anti-statictiecoat (and through any intervening layer between the conductive,anti-static topcoat and the electrically conductive multilayer stack) tothe metal layer of the electrically conductive multilayer stack (e.g., agold layer) and the p-static charge (or other electric charge) isdissipated by the metal layer (e.g., the gold layer) to reduce theamount of electric charge (e.g., p-static charge) on a surface of thecoated substrate.

The conductive, anti-static tiecoat and the conductive, anti-statictopcoat may each independently be formed from a coating compositioncapable of forming a coating providing p-static charge dissipation andhaving good weatherability and good resistance to acid rain, chemicals(e.g., solvents), salt-fog, abrasion and rain erosion. According toembodiments of the present disclosure, the conductive, anti-statictiecoat and the conductive, anti-static topcoat can each independentlybe formed from a coating composition including a hydrophobic firstaliphatic polyisocyanate, a second aliphatic polyisocyanate including ahydrophilic portion, a polyester polyol, a fluorinated polyol and afluorinated alcohol. The coating composition for forming the conductive,anti-static tiecoat further includes reactive salts (e.g., quaternaryammonium salts). The reactive salts included in the conductive,anti-static tiecoat improve the conductivity of the conductive,anti-static tiecoat. The coating composition for forming the conductive,anti-static tiecoat and the coating composition for forming theconductive, anti-static topcoat can each be reacted to form a coatingincluding a polyurethane polymer. Thus, as described herein, the coatingcan include the various components of the coating composition in theirreacted or unreacted forms, for example, the hydrophobic first aliphaticisocyanate and polyester polyol can be included in the coating in theirreacted forms (e.g., as monomers in a urethane or carbamate polymerlinkage). The hydrophobic components or portions described hereinprotect embodiments of the coated substrate from UV light and humidityand enhance the chemical resistance of the conductive, anti-statictiecoat to withstand normal hand-washing techniques encountered in theproduction and flow coating application of the conductive, anti-statictopcoat. The hydrophilic components or portions described herein promotestatic charge dissipation.

A variety of isocyanates and polyisocyanates (such as difunctional,polyfunctional, aromatic, aliphatic, monomeric and oligomericisocyanates) can be used in the coating composition to form polyurethanecoatings. Aliphatic isocyanates have good hydrolytic stability and UVresistance. Non-limiting examples of monomeric aliphatic diisocyanatesinclude hexamethylene diisocyanate, methylenebis-(4-cyclohexylisocyanate), and isophorone diisocyanate. Monomericaliphatic diisocyanates can be used to prepare polyisocyanate adducts,prepolymers and thermoplastic polyurethanes (“TPUs”). For example,monomeric aliphatic diisocyanates can be used to prepare biuret-basedpolyisocyanates (e.g., polyisocyanates including the—(HN—CO—)₂N-functional group), isocyanurate ring-based polyisocyanates(e.g., isophorone diisocyanate trimers), and other oligomers ofpolyisocyanates. More specifically, hexamethylene diisocyanate (HDI) canbe used to prepare the HDI-based biuret shown in Structure 1 below orthe HDI-based trimer including an isocyanurate ring shown in Structure 2below. Isophorone diisocyanate (IPDI) can be used to prepare theIPDI-based trimer shown in Structure 3 below, which is an isocyanuratering-based polyisocyanate. HDI trimers including an isocyanurate ringhave much lower viscosity than HDI-based biurets. IPDI trimers havelower reactivity than HDI trimers.

According to embodiments of the present disclosure, the first aliphaticpolyisocyanate can be one or more of a biuret-based polyisocyanate, anisocyanurate ring-based polyisocyanate, or an isophorone diisocyanateoligomer. For example, the first aliphatic polyisocyanate can includeone or more of the HDI-based biuret shown in Structure 1 above (or aderivative thereof), the HDI-based trimer including an isocyanurate ringshown in Structure 2 above (or a derivative thereof), or the IPDI-basedtrimer shown in Structure 3 above (or a derivative thereof).Non-limiting commercially available examples of the first aliphaticpolyisocyanate (or mixtures including the first aliphaticpolyisocyanate) include methylene bis-(4-cyclohexylisocyanate) (e.g.,DESMODUR® W), methylene 1,6-hexamethylene diisocyanate-basedpolyisocyanates (e.g., DESMODUR® N-75, DESMODUR® N-100, DESMODUR®N-3200, DESMODUR® N-3300, DESMODUR® N-3600, and DESMODUR® N-3790) andisophorone diisocyanate-based polyisocyanates (e.g., DESMODUR® Z-4470)(each available from Bayer Material Science). DESMODUR® is a registeredtrademark of Bayer Material Science, Leverkusen, Germany. Some of theforegoing examples include an aliphatic polyisocyanate dispersed in (ordiluted with) a solvent, which reduces the viscosity of thepolyisocyanate, thereby improving ease of handling the first aliphaticpolyisocyanate.

The first aliphatic isocyanate can have a functionality of 3 or more(e.g., have 3 or more isocyanate functional groups). In someembodiments, the first aliphatic polyisocyanate has an isocyanatefunctionality in a range of 3.0 to 4.2. For example, the first aliphaticpolyisocyanate can have an isocyanate functionality of about 3.2, 3.5,3.8 or 4.1. In some embodiments, for example, the first aliphaticpolyisocyanate can have an isocyanate functionality of about 3.8

According to embodiments of the present disclosure, a coatingcomposition including the first aliphatic polyisocyanate describedherein (e.g., an HDI biuret-based polyisocyanate) is capable of formingan elastic coating (or film) having good low temperature flexibility,thereby providing resistance to rain erosion that is not achieved withother polyisocyanates. The coating may also have good weatherability andmechanical strength. Some examples of the coating composition includingan HDI biuret-based polyisocyanate formed a coating having gooddurability, but reduced resistance to rain erosion. Some examples of thecoating composition including an isocyanurate ring-based polyisocyanate(e.g., an HDI trimer-based polyisocyanate) formed a coating having goodresistance to rain erosion, but reduced chemical (e.g., solvent)resistance. Some examples of the coating composition including anisocyanurate ring-based polyisocyanate formed a coating having arelatively short tack-free time and good chemical resistance, but, dueto the high T_(g) of the isocyanurate ring-based polyisocyanate (˜60°C.), the resultant coating was rigid and had poor resistance to rainerosion. In comparison, the T_(g) of some HDI biuret-basedpolyisocyanates (e.g., DESMODUR® N-75 and DESMODUR® N-100) is about −60°C.

According to embodiments of the present disclosure, the coatingcomposition further includes a second aliphatic polyisocyanate includinga hydrophilic portion. The hydrophilic portion of the second aliphaticpolyisocyanate can include a polyether chain. In some embodiments, thesecond aliphatic polyisocyanate further includes a hydrophobic portion.The hydrophobic portion of the second aliphatic isocyanate can includean isophorone diisocyanate moiety or a derivative thereof. Non-limiting,commercially available examples of the second aliphatic polyisocyanate(or mixtures including the second aliphatic polyisocyanate) includepolyether modified HDI trimer-based polyisocyanates (e.g., BAYHYDUR® 302and BAYHYDUR® 303), polyether modified HDI allophonate-basedpolyisocyanates (e.g., BAYHYDUR® 304, and/or BAYHYDUR® 305), isophoronediisocyanate-based hydrophilically modified aliphatic polyisocyanate(e.g., polyether modified isophorone diisocyanate trimer, such asBAYHYDUR® 2150BA and/or BAYHYDUR® 401-70), ionic aminosulfonic acidmodified HDI polyisocyanates (e.g., BAYHYDUR® XP2547, BAYHYDUR®XP2487/1, and/or BAYHYDUR® XP 2655) (each available from Bayer MaterialScience). BAYHYDUR® is a registered trademark of Bayer Material Science.The second aliphatic polyisocyanate can have a functionality of 2 ormore (e.g., 2 or more isocyanate functional groups).

An example of a polyether modified HDI trimer-based polyisocyanate(non-ionic) is shown as Structure 4 below, which is hydrophilic andreadily dispersible in water. Examples of the coating compositionincluding a polyether modified HDI trimer-based polyisocyanate(non-ionic) as the second aliphatic polyisocyanate formed coatingshaving enhanced anti-static properties, but the coatings exhibitedreduced integrity against certain tests such as the humidity test and50/50-water/IPA test. Accordingly, while these polyisocyanates may beused as the second aliphatic polyisocyanate, other polyisocyanates mayprovide better coating integrity.

An example of a polyether modified HDI allophonate-based polyisocyanateis shown as Structure 5 below, which is more hydrophobic than thepolyether modified HDI trimer-based polyisocyanates (non-ionic)described above, and has higher NCO functionality. Examples of thecoating composition including a polyether modified HDI allophonate-basedpolyisocyanate as the second aliphatic polyisocyanate formed coatingshaving enhanced film durability and resistance, but the coatingsexhibited reduced static charge dissipation, particularly at −40° F.Accordingly, while these polyisocyanates may be used as the secondaliphatic polyisocyanate, other polyisocyanates may provide bettercharge dissipation.

An example of an ionic aminosulfonic acid modified HDI polyisocyanate isshown as Structure 6 below, which has high NCO functionality. Ionicaminosulfonic acid modified HDI polyisocyanates (CAPS) are commerciallyavailable from Bayer Material Science as BAYHYDUR® XP2547, BAYHYDUR®XP2487/1, and BAYHYDUR® XP 2655. Examples of the coating compositionincluding an ionic aminosulfonic acid modified HDI polyisocyanate as thesecond aliphatic polyisocyanate formed coatings having good chemical(e.g., solvent) resistance, but the coatings exhibited minimalimprovement in anti-static properties. Accordingly, while thesepolyisocyanates may be used as the second aliphatic polyisocyanate,other polyisocyanates may provide better anti-static properties.

In some embodiments, the second aliphatic polyisocyanate includes apolyether modified IPDI trimer, which includes a polyether chain bondedto an isophorone diisocyanate trimer. An example of a polyether modifiedIPDI trimer-based polyisocyanate is shown as Structure 7 below. Examplesof the coating composition including a polyether modified IPDItrimer-based polyisocyanate as the second aliphatic polyisocyanateunexpectedly formed coatings having good film integrity as well as goodstatic charge dissipation properties. A commercial example of apolyether modified IPDI trimer-based polyisocyanate is BAYHYDUR® 401-70,which has a T_(g) of about 30° C., forms coatings having an improvedtime to tack-free (i.e., a shorter time to become tack-free), reducedsurface tackiness, and enhanced anti-static properties. However, whenexcessive amounts of polyether modified IPDI trimer-based polyisocyanateare included in the coating composition as the second aliphaticisocyanate, the coating formed from the coating composition exhibitsreduced resistance to rain erosion, increased sensitivity to humidity,and reduced Bayer abrasion resistance. Accordingly, in some embodiments,a weight ratio of the hydrophobic first aliphatic polyisocyanate to thesecond aliphatic polyisocyanate is in a range of 95:5 to 85:15, such as,for example, a ratio of 95:5, 92:8, 90:10, 87:13 or 85:15.

In some embodiments, the coating composition further includes apolyester polyol. For example, the polyester polyol can be an aliphaticcompound having 2 to 4 hydroxyl groups or a mixture of aliphaticcompounds having an average of 2 to 4 hydroxyl groups. The polyesterpolyol can provide crosslinking and resiliency to a coating formed fromthe coating composition. Non-limiting examples of the polyester polyolinclude polycaprolactone polyols and diols. For example, the polyesterpolyol can be a polycaprolactone polyol, polycaprolactone diol, ormixture thereof having a weight average molecular weight in a range of300 to 5,000 g/mole, for example, 500 to 1,500 g/mol, and in someembodiments, about 1,000 g/mol.

Polycaprolactone polyols and diols can be prepared using ring-openingpolymerization under mild conditions resulting in well-controlledpolymerization resulting in no or few byproducts (e.g., water).Polycaprolactone polyols and diols prepared using ring-openingpolymerization have low acid values, highly defined functionality, lowpolydispersity indexes and can be prepared with very highreproducibility. Polycaprolactone polyols and diols can also be preparedwith low levels of impurities, are non-toxic and biodegradable, and havehigh flexibility at low-temperatures, good hydrolytic stability, goodtear strength, consistent reactivity and low viscosity (as compared toother polyols). The high flexibility and good tear strength ofpolycaprolactone polyols and diols can impart resiliency to a coatingformed from a coating composition including a polycaprolactone polyoland/or polycaprolactone diol. Coatings having improved resiliencyexhibit enhanced Bayer abrasion (described in more detail below) andrain erosion resistance properties. Additionally, the low viscosity ofpolycaprolactone polyols and diols is beneficial for coatingcompositions having a high solids content. In some embodiments, thepolyester polyol includes a polycaprolactone polyol, a polycaprolactonediol or a mixture thereof.

In some embodiments, the polyester polyol is a polycaprolactone polyolincluding four hydroxyl groups. For example, the polyester polyol may bea polycaprolactone polyol including four polycaprolactone chains. Insome embodiments, each of the polycaprolactone chains includes one ofthe four hydroxyl groups at a terminal end of the polycaprolactonechain. An example of the polyester polyol (e.g., a polycaprolactonepolyol) is shown as Structure 8 below. In the polyester polyol shown asStructure 8, n may be in a range of 1 to 6, such as in a range of 2 to4. For example, in the polyester polyol shown as Structure 8, n may havean average value of 2. When the polyester polyol is a polycaprolactonepolyol including four polycaprolactone chains including one hydroxylgroup at a terminal end of each polycaprolactone chain, the coatingcomposition may form a coating having enhanced crosslink density, whichin turn improves the resistance of the coating to salt-fog and SO₂,chemicals (e.g., solvents), and inorganic acids (e.g., sulfuric acid andnitric acid). Additionally, the resultant coating may still havesuitable flexibility due to the presence of the caprolactone units(e.g., 1 to 6 units of caprolactone) in each of the four chains.

In some embodiments, the polyester polyol is a polyester diol. Thepolyester diol may be a linear aliphatic diol having a first endincluding a hydroxyl group and a second end including another primaryhydroxyl group. The primary hydroxyl groups may be connected by apolycaprolactone backbone. An example of the polyester polyol (e.g., apolycaprolactone diol) is shown as Structure 9 below. In the polyesterdiol shown as Structure 9, n may be in a range of 1 to 8, such as in arange of 2 to 6. For example, in the polyester polyol shown as Structure9, n may have an average value of 4.

When the coating composition includes a polyester polyol, such as apolycaprolactone diol, a coating formed from the coating composition hasenhanced resiliency. For example, the relatively long polycaprolactonebackbone between the hydroxyl groups may provide the coating withenhanced resiliency. Example embodiments of the coating prepared withoutthe polyester diol, but including another polyester polyol, exhibitedresistance to Bayer abrasion (described in more detail below) after 600strokes of about 3 to 4%, while example embodiments of the coatingprepared with the polyester diol exhibited resistance to Bayer abrasionof less than 1% after 600 strokes. Including the polyester diol in thecoating composition in excess increases the tackiness of coatings formedfrom the coating composition and reduces the chemical (e.g., solvent)resistance of the coating. Accordingly, in some embodiments, thepolyester polyol and the polyester diol are present in the coatingcomposition at a weight ratio of 95:5 to 50:50, for example at a weightratio 75:25. Non-limiting, commercially available examples of thepolyester polyol and the polyester diol include Capa™ 2101, Capa™ 3031,Capa™ 3041 and Capa™ 4101, each of which are available from PerstopGroup, Perstop, Sweden.

In some embodiments, the coating composition further includes afluorinated alcohol. For example, the fluorinated alcohol can have onereactive functional group (e.g., a hydroxyl group). By having onereactive group, the fluorinated alcohol can be a migratory fluorinatedcompound capable of migrating to a surface of the coating compositionduring formation (e.g., reaction or curing) of the coating. While theextent of the migration of the first fluorinated compound (e.g., themigratory fluorinated compound) is not fully known, based on the acidresistance of the coating formed from the composition and the observedcontact angle of water on the coating, it is believed that at least someof the fluorinated alcohol (e.g., the migratory fluorinated compound)migrates to the surface of the coating composition (e.g., the surface ofa coating formed from the coating composition).

It is believed that the migration of the fluorinated alcohol to thesurface of the coating composition (or the surface of the coating)improves the surface hydrophobicity of the resultant coating andenhances resistance of the coating to acid rain and humidity. In someembodiments, the fluorinated alcohol has a relatively low molecularweight to improve migration of the fluorinated alcohol. For example, thefluorinated alcohol may have a weight average molecular weight in arange of about 300 g/mole to about 400 g/mole, such as a weight averagemolecular weight of about 364 g/mole. The fluorinated alcohol caninclude a perfluorinated carbon chain and a hydroxyl group. Thefluorinated alcohol can also include a linking group between theperfluorinated carbon chain and the hydroxyl group. Non-limitingexamples of the linking group include alkylene groups, such as ethylene,propylene and vinylene groups, and sulfonamide groups.

According to embodiments of the present disclosure, a coating formedfrom the coating composition can include the fluorinated alcohol at asurface of the coating. By including the fluorinated alcohol at asurface of the coating, the hydrophobicity and acid resistance of thesurface of the coating are increased, thereby increasing the corrosionresistance of the coating. The presence of the fluorinated alcohol at asurface of the coating composition (or the coating) also increases thecorrosion resistance of a coated substrate including the coatingcomposition, for example, as a coating. The fluorinated alcohol may beincluded in the coating composition in an amount in a range of about 0.1wt % to about 5 wt %, for example, 1 wt %, based on the total weight ofthe solids content of the coating composition.

In some embodiments, the fluorinated alcohol is a partially fluorinatedcompound including a hydroxyl group. For example, in certain portions ofthe compound, most or all of the hydrogen atoms can be replaced withfluorine atoms, while other portions of the compound can includehydrogen bonded to carbon. In other embodiments, the fluorinated alcoholis a perfluorinated compound including a perfluorinated carbon backboneand a hydroxyl group. As would be understood by those of ordinary skillin the art, a “perfluorinated” compound (or chain) is a compound (orchain) in which all hydrogen atoms bonded to carbon atoms are replacedwith fluorine atoms. The fluorinated alcohol can have a carbon backbonehaving 1 to 20 carbon atoms.

Non-limiting examples of the fluorinated alcohol include perfluorinatedor partially fluorinated aliphatic compounds. For example, commerciallyavailable perfluorinated aliphatic compounds and/or solutions ofperfluorinated aliphatic compounds such as, for example,N-ethyl-N-(2-hydroxyethyl)perfluorooctylsulphonamide (e.g., FLUORAD™FC-10; available from 3M Company, St. Paul, Minn.); and3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol (e.g., CAPSTONE™62-AL), and perfluoroalkyl-1-ethanol (e.g., ZONYL® BA) (each availablefrom E.I. du Pont de Nemours and Company, Wilmington, Del.) can be used.ZONYL® is a registered trademark of E.I. du Pont de Nemours and Company.Examples of the fluorinated alcohol include Structures 10 and 11 below:

In some embodiments, the coating composition further includes afluorinated polyol. The fluorinated polyol can be a compound having acarbon backbone with 1 to 20 carbon atoms, and two or more reactivegroups, such as hydroxyl groups. That is, the fluorinated polyol can bemultifunctional. For example, the fluorinated polyol can bebifunctional, such as a compound having two or more hydroxyl groups. Asa result of having two or more reactive functional groups, thefluorinated polyol can react to form a three-dimensional network. Incontrast to the fluorinated alcohol, the majority of the fluorinatedpolyol does not migrate to a surface of the coating composition (or asurface of a coating formed from the composition) and instead isdistributed across the thickness of the coating composition or coating(e.g., is distributed throughout the bulk material of the coatingcomposition, or the bulk material of a coating formed from the coatingcomposition). The fluorinated polyol improves the bulk hydrophobicity ofa coating formed from the coating composition, thereby improving theacid rain resistance of the coating. Existing coatings (e.g., topcoats),such as FX-446 (available from PPG Industries Inc.), provide some acidrain resistance, but coatings according to embodiments of the presentdisclosure including the fluorinated polyol (or a reacted fluorinatedpolyol) in the bulk of the coating provide improved acid rain resistancecompared to existing coatings.

Inclusion of the fluorinated polyol causes the coating composition toform a three-dimensional polymer network. Specifically, the two or morereactive functional groups (e.g., hydroxyl groups) of the fluorinatedpolyol each react with other polymer molecules to form thethree-dimensional network structure. The rigidity of thethree-dimensional polymer network formed with the fluorinated polyolaffects the resiliency of a coating formed from the coating composition.Similarly, other components of the coating composition, such asnon-fluorinated polyols (e.g., the aliphatic polyester polyols), canalso form part of the three-dimensional network and contribute to theresiliency of a coating formed from the composition. As an example, therigidity of the three-dimensional network of the composition isinfluenced, in part, by the number of reactive functional groups (e.g.,hydroxyl groups) contained in the fluorinated polyol. Thus, the numberof reactive functional groups of the fluorinated polyol will affect theresiliency of a coating formed from the coating composition. Similarly,the number of reactive functional groups (e.g., hydroxyl groups)included in the non-fluorinated polyol (e.g., the polyester polyol) willalso affect the resiliency of a coating formed from the coatingcomposition.

In general, greater crosslink density (which is directly related to thenumber of reactive functional groups (e.g., hydroxyl groups) included ineach of the components of the composition) leads to greater rigidity,improved chemical and solvent resistance, and decreased abrasionresistance. The resiliency of a coating formed from the coatingcomposition is also influenced by the molecular weight, and size andtype of the backbone of the fluorinated and non-fluorinated compounds inthe coating composition. When the composition includes compounds thathave more rigid backbone structures, the composition will also be morerigid, while compounds that have relatively more flexible backbonestructures will produce a composition that has relatively moreresiliency. For a given polyol, increasing the molecular weight of thepolyol generally results in a compound that forms coatings havinggreater resiliency, as compared to the corresponding lower molecularweight polyols.

Accordingly, the desired resiliency of the composition can be achievedby appropriately selecting the number of reactive functional groups(e.g., hydroxyl groups) and molecular weights of the fluorinatedcompounds or the non-fluorinated compounds. For example, a fluorinatedpolyol having a fluorinated carbon backbone and two reactive functionalgroups (e.g., two hydroxyl groups) will form a three-dimensional networkthat is more flexible than the three-dimensional network formed by afluorinated polyol having similar chemical composition, the same (orsubstantially the same) molecular weight, and a fluorinated carbonbackbone and three reactive groups (e.g., three hydroxyl groups).Similarly, a fluorinated polyol having three reactive functional groups(e.g., three hydroxyl groups) will form a three-dimensional network thatis more flexible than the three-dimensional network formed by afluorinated polyol having the same (or substantially the same) chemicalstructure, the same (or substantially the same) molecular weight, afluorinated carbon backbone, but four reactive groups (e.g., fourhydroxyl groups). Increasing the flexibility of the three-dimensionalnetwork resulting from use of a fluorinated polyol having two hydroxylgroups increases the resiliency of a coating formed from the coatingcomposition. Thus, in some embodiments, the coating composition (orcoating) includes a bifunctional fluorinated polyol (e.g., a compoundhaving two hydroxyl groups), and such coating compositions producecoatings having increased resiliency over coatings produced from coatingcompositions including trifunctional or tetrafunctional fluorinatedpolyols (e.g., compounds having three or four hydroxyl groups,respectively). The above-described principles are also applicable toother components of the coating composition, such as the non-fluorinatedcompounds. For example, desirable resiliency of the coating) can beachieved using an appropriate mixture of non-fluorinated di-functionaland tetra-functional polyester polyols in the coating composition.

Non-limiting examples of the fluorinated polyol include fluoropolymersand fluoropolymer precursors, examples of which include, but are notlimited to, commercially available pure resins and/or solutions offluoropolymers and/or fluoropolymer precursors such as LUMIFLON® LF600X, LUMIFLON® LF 9716, LUMIFLON® LF 9721, LUMIFLON®-910LM andLUMIFLON® LF 916F (available from AGC Chemicals Inc., Exton, Pa.);FLUOROLINK® D10-H, FLUOROLINK® E10-H, FLUOROLINK® D, FOMBLIN® ETX,FOMBLIN® MF-402 and FLUOROBASE Z-1030 (each available Solvay Solexis,Inc.); and POLYFOX® PF-656 and POLYFOX® PF-7002 (available from OmnovaSolutions, Fairlawn, Ohio). LUMIFLON® is a registered trademark of AsahiGlass Co., Ltd., FLUOROLINK® is a registered trademark of SolvaySolexis, Inc. FOMBLIN® is a registered trademark of Solvay FluoratiHolding S.P.A., Corporation and POLYFOX® is a registered trademark ofAmpac Fine Chemicals LLC.

Of the foregoing examples of the fluorinated polyol, LUMIFLON®-910LM,which is a fluoroethylene vinyl ether, exhibited the best compatibilitywith the other components of the coating composition. LUMIFLON®-910LMwas compatible with the other components of the coating compositionthroughout a wide range of amounts. The alternating fluoroethylene andvinyl ether segments of LUMIFLON®-910LM provide the resultant coatingwith good weatherability. For example, the fluoroethylene segments mayenhance durability and hydrophobicity of the resultant coating.Accordingly, in some embodiments, the fluorinated polyol includes abackbone including alternating substituted or unsubstitutedfluoroethylene and substituted or unsubstituted vinyl ether segments. Anexample of the fluorinated polyol is shown as Structure 12 below, inwhich “FE” indicates a repeating fluoroethylene unit and “VE” indicatesa repeating vinyl ether unit. In Structure 12, R₁ may providetransparency, gloss and hardness; R₂ may provide flexibility; R₃ mayprovide crosslinking ability; and R₄ may provide adhesion.

The fluorinated polyol can be included in the coating composition in anamount in a range of about 5 wt % to about 35 wt %, such as in a rangeof about 15 wt % to about 25 wt %, based on the total weight of thesolids in the coating composition. In some embodiments, the fluorinatedpolyol is present in an amount of about 20 wt % based on the totalweight of the solids in the coating composition. At 5 wt % and 10 wt %of the fluorinated polyol, there was some improvement in the acidresistance of the resultant coating. At 15 wt % and 20 wt % of thefluorinated polyol, the resultant coating exhibited substantiallyenhanced resistance to sulfuric acid and nitric acid (e.g., a 50:50mixture of sulfuric acid and nitric acid) as compared to existingcoatings, such as FX-446. The resultant coating also exhibited improvedsurface tackiness and steam, humidity and QUV resistance as compared toexisting coatings, such as FX-446. Unexpectedly, the fluorinated polyoldid not noticeably reduce the anti-static properties of the coating.However, the fluorinated polyol does reduce the Bayer abrasionresistance of the resultant coating. For example, one example of thecoating composition including 20 wt % of the fluorinated polyol (basedon the total weight of the solids in the coating composition) formed acoating that exhibited a change in haze of 3.5-4.0% after 600 strokes ofthe Bayer abrasion test (described in more detail below), while anexample of the coating composition that did not include the fluorinatedpolyol exhibited a change in haze of about 1% after 600 strokes of theBayer abrasion test.

The coating composition described herein can be formed by mixing (orblending) a Part A mixture (e.g., a base component) with a Part Bmixture (e.g., a curing component). For example, the Part A mixture andthe Part B mixture can be mixed together and cured to form a durablecomposition (or coating) which is highly weatherable, abrasionresistant, acid resistant and resistant to chemicals or solvents. Aftermixing the Part A mixture and the Part B mixture, the resultant coatingcomposition can be air dried for a time period in a range of 1.5 to 2hours and then cured at about 200° F. for a time period of about 5 hoursto form a coating. For example, the coating composition (or coating) canform a polyurethane coating having anti-static properties.

The Part A mixture and Part B mixture may be mixed to achieve a ratio ofreactive isocyanate groups to reactive hydroxyl groups (e.g., an NCO toOH ratio) in a range of 1.05 to 1.5, such as a ratio of about 1.3. AnNCO to OH ratio of about 1.05 resulted in a coating exhibiting goodabrasion resistance, but compromised QUV resistance (described in moredetail below). An NCO to OH ratio of about 1.3 resulted in a coatingexhibiting good abrasion resistance, good QUV resistance, and goodresistance to rain erosion. An NCO to OH ratio of about 1.4 resulted ina coating exhibiting good QUV resistance, but lower abrasion resistanceand inferior resistance to rain erosion, as compared to the coatingformed from the coating composition having an NCO to OH ratio of about1.3. An NCO to OH ratio of about 1.5 resulted in a coating compositionhaving a short pot life, poor surface flow and poor cosmetics.

The Part A mixture can include a mixture of selective polyols, such as amixture of hydroxyl containing components having different aliphatic,fluorinated and non-fluorinated backbones having one or more reactivegroups, reactive and/or migratory ant-static agents, and reactive and/ormigratory UV absorbers/stabilizers. For example, the Part A mixture caninclude any or all of the polyester polyol (e.g., the first and/orsecond polyester polyol), the fluorinated polyol, the hydrophilic polyoland the fluorinated alcohol. The Part A mixture can further includeadditives, such as, for example, a migratory ultraviolet light (UV)absorber, a reactive UV absorber including a hydroxyl group, a migratoryUV stabilizer, a reactive UV stabilizer including a hydroxyl group, anantistatic agent (e.g., a conductive compound), an antioxidant, acatalyst, a flow control agent and/or a solvent. However, the Part Amixture need not contain each of these components. The Part A mixturecan include additional additives as well.

A migratory UV absorber and/or a reactive UV absorber may be included inthe coating composition to absorb UVA and UVB radiation incident to theresultant coating. UV absorbers increase the resistance of the resultantcoating to yellowing and/or degradation, and improve long term outdoordurability of the coating. The migratory UV absorber and reactive UVabsorber can be based upon any suitable UV absorber. The migratory UVabsorber does not include a reactive functional group (e.g., a hydroxylgroup) and migrates to a surface of the coating composition (or coating)during the formation (e.g., curing) of the coating composition (orcoating). By including the migratory UV absorber, the coating includes ahigher concentration of UV absorber at the surface of the compositionthan a coating not including a migratory UV absorber. Having a higherconcentration of UV absorber at the surface of the composition (orcoating) improves the lifetime of the coating made from the composition.However, it is desirable to also have UV absorber in the bulk of thecomposition, as having UV absorbers both at the surface of thecomposition and in the bulk of the composition will extend the lifetimeof a coating made from the composition as compared to a coating madefrom a composition that only includes UV absorber at the surface.

Additionally, if the compounds migrate to a surface of the compositiontoo quickly, the composition may form haze. For example, UV absorbersthat do not include a hydroxyl group (e.g., a reactive hydroxyl group)may migrate to the surface of the coating too quickly resulting in haze.Accordingly, in some embodiments, the coating composition includes themigratory UV absorber only in small amounts (e.g., in a range of about0.5 wt % to about 0.75 wt % based on the total weight of the solids ofthe coating composition), if at all. Examples of migratory UV absorbersare shown as Structures 13-17 below.

A coating composition according to embodiments of the present disclosurecan include a reactive UV absorber as well as, or instead of, themigratory UV absorber. The reactive UV absorber can include one or morereactive functional groups, such as a hydroxyl group. By including thereactive groups, a majority of the reactive UV absorber does not migrateto the surface of the coating composition or the resultant coating andinstead is distributed across the thickness of the coating compositionor resultant coating (e.g., is distributed throughout the bulk of thecoating composition or the resultant coating). Additionally, if thereactive UV absorber is multifunctional, it may contribute to thethree-dimensional polymer network formed on reaction of the componentsof the composition. A non-limiting example of the reactive UV absorberis shown as Structure 18 below, and an example of a commerciallyavailable mixture of a migratory UV absorber and a reactive UV absorberis shown as Structure 19 below.

Non-limiting commercially available examples of the migratory UVabsorber and reactive UV absorber include propanoic acid,2-[4-[4,6-bis([1,1′-biphenyl]-4-yl)-1,3,5-triazin-2-yl]-3-hydroxyphenoxy]-,isooctyl ester (e.g., TINUVIN® 479),β-[3-(2-H-benzotriazole-2-yl)-4-hydroxy-5-t-butylphenyl]-propionicacid-poly(ethylene glycol) 300 ester, bis{β-[3-(2-H-benzotriazole-2-yl)-4-hydroxy-5-t-butylphenyl]-propionicacid}-poly(ethylene glycol) 300 ester (e.g., TINUVIN® 1130), TINUVIN®477 and2-[4-[(2-hydroxy-3-(2′-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine(e.g., TINUVIN® 405) (each available from BASF Resins); andp-phenylenebis(methylenemalonic acid)tetraethyl ester (e.g., HOSTAVIN®B-CAP), 2-ethyl, 2′-ehtoxy-oxalanilide (e.g., HOSTAVIN® VSU), andpropanedioic acid, 2-[(4-methoxyphenyl)methylene]-, 1,3-dimethylester(e.g., HOSTAVIN® PR-25) (each available from Clariant InternationalLtd.). TINUVIN® is a registered trademark of Ciba Specialty ChemicalCorporation. HOSTAVIN® is a registered trademark of Hoechst GMBHCorporation.

Example coatings formed from coating compositions including the UVabsorber according to Structure 18 exhibited no discernible sign of hazeformation. It is believed that the presence of the hydroxyl group of theforegoing reactive UV absorbers prevented (or reduced) the migration ofthe UV absorbers to the surface of the coating by reacting withisocyanate functional groups to form urethane linkages and becoming partof the three-dimensional network, thereby preventing (or reducing) theformation of haze. TINUVIN® 1130 includes both a reactive UV absorberand a migratory UV absorber and, therefore, may cause haze in thecoating when used in excess. The migratory UV absorber may be includedin the coating composition in a small amount without causing haze in theresultant coating. For example, the migratory UV absorber shown asStructure 13 can be included in the coating composition in an amount ina range of about 0.5 wt % to about 0.75 wt % based on the total weightof the solids of the coating composition without causing noticeable hazein the resultant coating, while also enhancing the QUV resistance of theresultant coating. It is believed that the migratory UV absorber shownas Structure 13 will be present at a higher concentration at the surfaceof the resultant coating than in the bulk material of the coating,thereby providing additional protection against UV light. Some UVabsorbers, such as HOSTAVIN® B-CAP, exhibited poor solubility as aresult of poor compatibility with the other components of the coatingcomposition.

The migratory UV stabilizer and reactive UV stabilizer can be based uponany suitable UV stabilizer, such as any suitable free radical scavenger,that has been modified to be reactive or migratory. The migratory UVstabilizer and reactive UV stabilizer reduce degradation of the coatingby UV light by scavenging free radicals formed by the dissociation ofchemical bonds as a result of UV light absorption. The migratory UVstabilizer does not include a reactive functional group (e.g., ahydroxyl group) and migrates to the surface of the coating during theformation (e.g., curing) of the coating. By including the migratory UVstabilizer, the coating includes a higher concentration of the UVstabilizer at the surface of the coating than does a coating notincluding a migratory UV stabilizer. Having a higher concentration of UVstabilizer at the surface of the coating improves the lifetime of thecoating, and hence improves the lifetime of a coating formed from thecoating composition.

However, it is desirable to also have UV stabilizers in the bulk of thecoating, as having UV stabilizers both at the surface of the coating andin the bulk of the coating will extend the lifetime of the coating ascompared to a coating that only includes UV stabilizers at the surface.Additionally, if the compounds migrate to a surface of the coating tooquickly, the coating may develop a haze. Accordingly, a compositionaccording to embodiments of the present disclosure can include thereactive UV stabilizer, the migratory UV stabilizer or both. Thereactive UV stabilizer can include one or more reactive functionalgroups, such as a hydroxyl group. By including the reactive groups, amajority of the reactive UV stabilizer does not migrate to a surface ofthe coating and instead remains in the interior of the coating (e.g., inthe bulk material of the coating) due to reaction of the reactivefunctional groups with other components of the coating composition.Additionally, if the reactive UV stabilizer is multifunctional, it maycontribute to the formation of the three-dimensional network.Non-limiting commercially available examples of the UV stabilizerinclude propanedioic acid[(4-methoxyphenyl)-methylene]-bis(1,2,2,6,6-pentamethyl-4-piperidinyl)ester(e.g., HOSTAVIN® PR-31 available from Clariant International Ltd.),Sanduvor 3055 (available from Clariant International Ltd.) andcommercially available hindered aminoether light stabilizers such asTINUVIN® 123, TINUVIN® 292, TINUVIN® 326, TINUVIN® 328, TINUVIN® 765,TINUVIN® 900, TINUVIN® 900 and TINUVIN® 152 (each available from BASFResins). TINUVIN® is a registered trademark of Ciba Specialty ChemicalCorporation. HOSTAVIN® is a registered trademark Hoechst GMBHCorporation. Examples of reactive UV stabilizers and migratory UVstabilizers are shown as Structures 20-29. Example coatings formed fromexamples of coating compositions including the UV stabilizer accordingto Structure 21 exhibited no discernible sign of haze formation.

The Part A mixture can include anti-static agents (e.g., conductivecompounds, such as conductive metal oxides, quaternary ammonium salts,inherently conductive polymers, and/or other suitable conductiveagents), such as those described in U.S. Patent Application PublicationNo. 2010/0025533 and U.S. Patent Application Publication No.2010/0028684, the entire contents of which are incorporated herein byreference. Non-limiting commercially available examples of theanti-static agents include Antistat SD100 (available from E.I. du Pontde Nemours and Company), EA Antistat (available from Wells PlasticsLtd), and MAXOMER® AS-1018/75DC (available from PCC Chemax, Inc.).MAXOMER® is a registered trademark of PCC Chemax, Inc.

The anti-static agents (e.g., conductive compounds) can be used toreduce the electrical resistance (e.g., sheet resistance) of theresultant coating to levels acceptable for P-static dissipation, whichshould be maintained even at low temperatures (e.g., −40° F.). Thehydrophilic polyisocyanates discussed above can act as a conductivecompound. Alternatively or additionally, a hydrophilic polyol may beincluded in the coating composition.

For example, the coating described herein can have a sheet resistancesuch that electric charge (e.g., P-static) can pass through the coatingto another layer (e.g., an electrically conductive stack), which canthen dissipate or drain the charge. If the resistance of the coating istoo high, the amount of electric charge that can pass through thecoating is reduced, and the conductive layer will not provide acceptablelevels of P-static dissipation. In some embodiments, a primer layer(e.g., a polyacrylate primer) may be included between the coating andthe conductive layer (e.g., the electrically conductive multilayerstack). Although the primer layer may have a high sheet resistance(e.g., higher than that of the coating), charge may still pass throughthe coating and the primer layer to the conductive layer if the primerlayer is sufficiently thin. Thus, if a primer layer is included itshould be made sufficiently thin to allow enough electric charge to passthrough the coating and the primer layer to the conductive layer toprovide P-static dissipation.

The general electrical resistance of the coating (the conductive,anti-static tiecoat and the conductive, anti-static topcoat) is morethan or equal to 10¹²Ω/□ to independently dissipate the static charge.The sheet resistance of the coatings described herein varies dependingupon the sheet resistance of the material on which the coating isformed. For example, if the coating is on a dielectric layer (e.g.,polycarbonate), the sheet resistance of the coating may be about 10⁹ohms per square, even if a thin primer layer is included between thecoating and the dielectric layer. If the coating is on a conductivelayer (e.g., a titanium oxide/Au/titanium oxide stack), the sheetresistance of the coating may be 10⁷ ohms per square.

Hydrophilic polyisocyanates, such as those described above, improveconductivity in the coatings. Additionally, as described above,hydrophobic polyisocyanates provide coatings with durability. Thus, asdescribed above, through the combination of hydrophobic and hydrophilicpolyisocyanates (e.g., hydrophobic/hydrophilic HDI and IPDI basedpolyisocyanates), a coating having a good balance of hardness,resiliency, surface tackiness, and conductivity can be obtained.

According to some embodiments, the coating composition may furtherinclude a hydrophilic polyol (e.g., a reactive anti-static resin), suchas hydrophilic polyol having a functionality of more than 2. Thep-static properties of a coating can be significantly improved byintroduction of the hydrophilic polyol. The hydrophilic polyol can beany suitable hydrophilic polymer having salt moieties and pendantreactive hydroxyl groups. One non-limiting example of a suitablehydrophilic polyol is Superstat 463, which is commercially availablefrom Advanced Materials & Coating Specialties, Azusa, Calif. Thehydrophilic polyol reacts with the polyisocyanates and becomes part ofthe three dimensional network. A clear coating is then formed with nodiscernible sign of migration of the hydrophilic polyol to the surfaceof the coating. It is believed that the conductivity is achieved bymoisture absorption in the coating, but the hydrophilic polyol appearsto have some inherent conductivity.

A coating having an electrical resistance of 10⁵Ω/□ (on polycarbonate)and good optics is formed when the combined amount of the polyesterpolyol and the hydrophilic polyol includes 50 wt % of Superstat 463.Such a coating has good performance in p-static tests, even at −40° F.The hydrophilic polyol (e.g., Superstat 463) may be included in thecoating composition in an amount in a range of about 5 wt % to about 30wt % based on the total weight of the solids of the coating composition.When the hydrophilic polyol (e.g., Superstat 463) is included in thecoating composition in an amount that is outside of the foregoing range(e.g., is higher than 30 wt %), the resultant coating may have highsurface tackiness and may be susceptible to moisture attack when exposedto humidity. The surface tackiness can be reduced by the addition of BYK3700 (a polydimethylsiloxane resin with pendant hydroxyl groups),incorporation of ethylene glycol or trimethylol propane (TMP), and/orpartial replacement of N-75 with IPDI trimer. None of these improvementsin surface tackiness yielded a coating having good weatherability, butsome of the coatings did exhibit good abrasion resistance.

Useful anti-static coatings were formulated by reducing the hydrophilicpolyol (e.g., Superstat 463) content down to a range of 14 wt % to 26 wt%. A typical two-part polyurethane coating has a resistance of more than10¹² ohms/sq. and is dielectric. By addition of 14 to 24 wt % Superstat463 (depending upon the other components of the coating composition),the resistance is reduced to between the range of 10⁸ to 10⁹ ohms/sq. onpolycarbonate and 10⁷ to 10⁸ ohms/sq. on a conductive layer, such as astack including titanium oxide/Au/titanium oxide, a stack includingAZO/Au/AZO, an ITO layer, a Au layer, an Al layer, and the like. It hasrepeatedly been demonstrated, by the results of specification tests,that a combination of conductive layer/primer/conductive, anti-statictiecoat/conductive, anti-static topcoat can readily dissipate p-staticcharge even at temperatures as low as −40° F.

Superstat 463 can enhance the conductivity of the coating. Superstat 463is compatible with all components of the coating composition and gives acoating having high transparency, low haze, good surface flow, andsuperior cosmetics. Interestingly, without the presence of Superstat463, the coating composition may exhibit poor film-forming properties.Therefore, Superstat may be beneficial in enhancing the compatibilityamong the hydrophilic/hydrophobic components of the coating composition.

The Part A mixture can further include a catalyst, a flow control agentand solvents available in the art. Selection of a suitable catalyst,flow control agent and solvent is within the skill of those of ordinaryskill in the art and, therefore, further discussion of those componentsis not necessary here.

The Part B mixture (e.g., curing component) can include the isocyanateas described above. For example, the Part B mixture (the curingcomponent) can include selective isocyanates, such as an aliphatichydrophobic polyisocyanate and an aliphatic hydrophilic polyisocyanate.The curing component can further include cure accelerators, cureretardants, plasticizers, additives, and/or fillers. However, like thePart A mixture, the Part B mixture need not contain each of thesecomponents. The Part B can include additional additives as well.Selection of suitable cure accelerators, cure retardants, plasticizers,additives, and fillers is within the skill of those of ordinary skill inthe art and, therefore, further discussion of those components is notnecessary here.

According to embodiments of the present disclosure, the coatingcomposition includes at least one solvent. The solvent(s) may be addedto the Part A mixture, the Part B mixture, or both the Part A mixtureand the Part B mixture. The solvent(s) reduce the viscosity of thecoating composition to make it flow-coatable. The integrity andappearance of the resultant coating can be affected by the nature of thesolvents used, even though the solvents are not a permanent component ofthe cured coating. The evaporation rate of the solvent (or solventmixture) can be adjusted so that evaporation takes place quickly duringthe initial drying (e.g., after flow coating) to prevent excessive flow,but slowly enough to give sufficient leveling and adhesion. Thesolvent(s) used can be non-reactive with isocyanates and non-aggressiveagainst the substrate and/or coated surfaces, so that no (or little)attack takes place during the flow coating and/or airdrying process. Thesolvent(s) could also influence the rate of isocyanate-hydroxylreactions, for example during the airdrying period, depending on theextent of hydrogen bonding and dipole moment character of the solvent.

Non-limiting examples of the solvent include isobutyl acetate,2,6-dimethyl-4-heptanol, butoxy ethyl acetate, isobutyl acetate,2-butoxyethyl acetate, diisobutyl ketone, dipropyleneglycol dimethylether, and propyleneglycol dimethyl ether. In some embodiments, thesolvent includes diacetone alcohol (DAA). DAA has a slow evaporationrate and good flow properties. DAA effectively dissolves all (or most)of the components of the coating composition to give a clear,homogeneous solution. DAA has a tertiary hydroxyl group, but thereactivity of the tertiary hydroxyl with isocyanate is much lower thanthe hydroxyls of the other components of the coating composition, andsince DAA begins to evaporate during the airdrying period, the reactionof DAA with the polyisocyanates is negligible.

The solvent may also be used to adjust the solids content of the coatingcomposition. It may be beneficial to maximize the thickness of theresultant coating for improved performance in the rain erosion test. At70% solids content the coating composition is too viscous for successfulflow coating application with existing equipment. At a solids content of65%, the coating composition forms a coating that is free from cosmeticdefects, has good surface quality, and provides good performance in therain erosion test. A coating composition having a 65% solids contentapplied to a production F-22 test canopy by a two component mixer (e.g.,a mixer, such as the DL 2 mixer, available from Liquid Control Ltd.,Wellingborough, England) formed a coating having good surface quality.Offcuts from the test canopy had no apparent damage after 44 minutes ofrain erosion testing at 550 mph.

As described above, the coating composition can be used to form thecoating. For example, a coated substrate 100 (e.g., a coatedtransparency) is shown in FIG. 1. As can be seen in the embodiment shownin FIG. 1, the coated substrate 100 (coated transparency) includes thesubstrate 10, the conductive, anti-static tiecoat 107 on the substrate,and the conductive, anti-static topcoat 105 on the conductive,anti-static tiecoat. In this embodiment, the conductive, anti-statictiecoat 107 and the conductive, anti-static topcoat 105 may each beformed from the coating composition described herein. The coatedsubstrate can be used as a windshield, window, or canopy of an aircraft,but the present disclosure is not limited thereto. For example, thecoated substrate can also be used as a window or windshield of a car,aircraft, boat, building, or any other suitable vehicle or structure. Inthe case of a modern aircraft canopy, the substrate may be an organicresin, such as polycarbonate or polyacrylate.

It is understood that the present disclosure is not limited to theconfiguration shown in FIG. 1, and there can be one or more additionalintervening layers or features between the substrate 10 and theconductive, anti-static topcoat 105. In FIG. 1, the conductive,anti-static topcoat 105 is the outer most layer of the coated substrate,and is a tough, durable and weather resistant material, such aspolyurethane, yet is sufficiently pliable and flexible to prevent crackformation due to thermal stress. As described above, the coatingcomposition, and therefore the coating, can include conductive compoundsto provide anti-static properties, and the coating can be conductive tohelp dissipate static charge and other electromagnetic forces. Forexample, the coating can have antistatic properties to allow staticcharge to be dissipated to underlying conductive layer(s), if present.In some embodiments, the conductive, anti-static tiecoat and theconductive, anti-static topcoat each independently include otheradditives such as those described in U.S. Patent Application PublicationNo. 2010/0025533 and U.S. Patent Application Publication No.2010/0028684 (e.g., conductive metal oxides, quaternary ammonium salts,inherently conductive polymers, and/or other suitable conductiveagents). In some embodiments, the conductive, anti-static tiecoat and/orthe conductive, anti-static topcoat is substantially free of inherentlyconductive polymers, ionic liquids, conductive oxides (e.g., conductivemetal oxides), and carbon nanotubes (CNT). As used herein, the terms“substantially free of inherently conductive polymers, ionic liquids,conductive oxides (e.g., conductive metal oxides), and carbon nanotubes(CNT)” and like terms are used as terms of approximation (not as termsof degree) to denote that the amount of inherently conductive polymers,ionic liquids, conductive oxides (e.g., conductive metal oxides), orcarbon nanotubes (CNT) in the conductive, anti-static tiecoat and/or theconductive, anti-static topcoat is at most negligible, such that if theinherently conductive polymers, ionic liquids, conductive oxides (e.g.,conductive metal oxides), or carbon nanotubes (CNT) are present at allin the conductive, anti-static tiecoat and/or the conductive,anti-static topcoat, it is present as an incidental impurity. In someembodiments, the conductive, anti-static tiecoat and/or the conductive,anti-static topcoat is completely free of inherently conductivepolymers, ionic liquids, conductive oxides (e.g., conductive metaloxides), and carbon nanotubes (CNT). For example, under certainconditions, inherently conductive polymers, ionic liquids, conductiveoxides (e.g., conductive metal oxides), or CNT are not suitable due to alack of compatibility with the conductive, anti-static tiecoat and/orthe conductive, anti-static topcoat, due to a significant reduction inthe light transmission of the conductive, anti-static tiecoat and/or theconductive, anti-static topcoat, and/or due to a resultant intensecoloration of the conductive, anti-static tiecoat and/or the conductive,anti-static topcoat

The electrically conductive multilayer stack of the coated substrate caninclude first and second metal oxide layers including titanium oxide,the first metal oxide layer including a first region (e.g., a firstsub-layer), a second region (e.g., a second sub-layer) on the firstregion, and a third region (e.g., a third sub-layer) on the secondregion, the first region and the third region each having a higheroxygen concentration than that of the second region, and a metal layer(such as a metal layer including gold (Au)) between the first and secondmetal oxide layers. The first metal oxide layer can be positioned overthe transparency, and the metal layer can be positioned between thefirst metal oxide layer and the second metal oxide layer. As usedherein, the term “titanium oxide” refers to any compound containing onlyTi and O as the constituent elements. Some non-limiting examples ofsuitable titanium oxides include TiO₂, TiO, Ti₂O₃, Ti₃O, Ti₂O, andderivatives or variations thereof.

A coated substrate (e.g., a coated transparency) including such anelectrically conductive multilayer stack is shown in FIG. 2. As can beseen in the embodiment of FIG. 2, the coated substrate 200 includes asubstrate 10 or transparency (such as an aircraft canopy), and anelectrically conductive multilayer stack 120. The electricallyconductive multilayer stack includes a first metal oxide layer 40including titanium oxide adjacent to a metal layer 50, and a secondmetal oxide layer 60 including titanium oxide adjacent to the metallayer 50. Each of the first and second metal oxide layers and the metallayer can be positioned on or over an adjacent layer in the order shown.One or more of the first metal oxide layer 40 and the second metal oxidelayer 60 can include various regions (or sub-layers) as described inmore detail below. The coated transparency can also include additionallayers, such as tie, base, and topcoat layers, as desired. For example,although the conductive, anti-static topcoat 105 according toembodiments of the present disclosure can be used as a topcoat, in someembodiments, the conductive, anti-static topcoat may be used as a baselayer or other coating with one or more additional layers on top of theconductive, anti-static topcoat 105.

At least one of the first metal oxide layer and the second metal oxidelayer includes a first region, a second region on the first region, anda third region on the second region. The first region and the thirdregion each have a higher oxygen concentration than that of the secondregion. For example, an embodiment in which the first metal oxide layer40 includes a first region 40 a, a second region 40 b, and a thirdregion 40 c is shown in FIG. 3. As can be seen in the embodiment in FIG.3, the second region 40 b is on the third region 40 c, and the firstregion 40 a is on the second region 40 b. Alternatively, the secondregion 40 b can be on the first region 40 a, and the third region 40 ccan be on the second region 40 b. However, it is understood that thefirst, second and third regions 40 a, b and c can be positioned in anyorder relative to each other, and are not limited to the positions andorder described here and depicted in the drawings.

FIG. 4 shows another embodiment in which the second metal oxide layer 60includes a first region 60 a, a second region 60 b, and a third region60 c. As can be seen in the embodiment in FIG. 4, the second region 60 bis on the third region 60 c, and the first region 60 a is on the secondregion 60 b. Alternatively, the second region 60 b can be on the firstregion 60 a, and the third region 60 c can be on the second region 60 b.FIG. 5 shows another embodiment in which each of the first metal oxidelayer 40 and the second metal oxide layer 60 include a first region, asecond region, and a third region. The first region and the third regioneach have a higher oxygen concentration than that of the second region.

According to embodiments of the present disclosure, a method ofmanufacturing an electrically conductive multilayer stack includes:forming a first metal oxide layer including titanium oxide; forming ametal layer on the first metal oxide layer; and forming a second metaloxide layer including titanium oxide on the metal layer, at least one ofthe forming the first metal oxide layer and the forming the second metaloxide layer including forming a first region, a second region and athird region, the first region and the third region each having a higheroxygen concentration than the second region. The metal oxide layers canbe prepared using any suitable process capable of producing a metaloxide layer including a first region, a second region and a thirdregion, the first region and the third region each having a higheroxygen concentration than the second region. For example, the metaloxide layers can be prepared using physical vapor deposition, atomiclayer deposition, and chemical vapor deposition (e.g., plasma enhancedchemical vapor deposition). Additionally, the first region, secondregion and third region can be formed after the deposition of thecorresponding metal oxide layer. For example, the metal oxide layer canbe deposited first and then subjected to a post deposition treatment tocreate the first region, second region and/or third region.

In some embodiments, at least one of the first metal oxide layer or thesecond metal oxide layer is formed by varying a flow rate of oxygenduring formation. The metal oxide layers can be formed by any suitableprocess, such as, for example, a physical vapor deposition process suchas sputtering. The sputtering can include, for example, sputtering froma titanium metal target or TiO₂ target, but the present disclosure isnot limited thereto. In some embodiments, both of the first metal oxidelayer and the second metal oxide layer are formed by varying the flowrate of oxygen during formation (e.g., while sputtering). By varying theflow rate of oxygen during formation, the oxygen concentration of themetal oxide layer can be varied, thereby forming an oxygen concentrationgradient in the formed layer. The different oxygen concentrations in thegradient forming the first, second and third regions of the first metaloxide layer or the second metal oxide layer.

For example, varying the flow rate of oxygen while sputtering caninclude flowing oxygen at a first oxygen flow rate, then flowing oxygenat a second oxygen flow rate, and then flowing oxygen at a third oxygenflow rate. In some embodiments, a ratio of the first oxygen flow rate tothe second oxygen flow rate is in a range of about 10:1 to about 25:1,and a ratio of the third oxygen flow rate to the second oxygen flow rateis in a range of about 10:1 to about 25:1. By varying the oxygen flowrate during formation, the first or second metal oxide layer is formedwith first, second and third regions, each region having a differentoxygen concentration. Additionally, as described in more detail below,varying the oxygen flow rate can also vary the surface roughness of thefirst region, the second region, and the third region, thereby varyingthe surface area of each. For example, forming a region of titaniumoxide while flowing oxygen at a higher flow rate results in an increasedsurface area (or surface energy) as compared to forming a region oftitanium oxide while flowing oxygen at a lower flow rate. The increasedsurface area of a region of titanium oxide formed at higher oxygen flowrate can be observed using transmission electron microscopy (TEM), underwhich the region of titanium oxide will exhibit a wavier cross-sectionas compared to a region of titanium oxide formed at a lower flow rate ofoxygen, which will exhibit a smoother cross-section under TEM.

In some embodiments, varying the flow rate of oxygen during formation(e.g., while sputtering) further includes flowing a first inert gas at afirst inert gas flow rate, then flowing a second inert gas at a secondinert gas flow rate, and then flowing a third inert gas at a third inertgas flow rate. For example, a ratio of the first oxygen flow rate to thefirst inert gas flow rate can be in a range of about 0.8:2.2 to about1:1.8, a ratio of the second oxygen flow rate to the second inert gasflow rate can be in a range of about 1:29 to about 2:25, and a ratio ofthe third oxygen flow rate to the third inert gas flow rate can be in arange of about 0.8:2.2 to about 1:1.8. By flowing inert gases at theforegoing flow rates, the oxygen concentration of the first region, thesecond region, or the third region can be further controlled.

In some embodiments, flowing inert gas at the first inert gas flow rateis performed simultaneously with flowing oxygen at the first oxygen flowrate, flowing inert gas at the second inert gas flow rate is performedsimultaneously with flowing oxygen at the second oxygen flow rate, andflowing inert gas at the third inert gas flow rate is performedsimultaneously with flowing oxygen at the third oxygen flow rate. Thefirst, second and third inert gases can be the same or different. Insome embodiments, each of the first inert gas, second inert gas and thethird inert gas are all the same (e.g., Ar).

The duration of the deposition process will depend upon the depositionprocess being used and the characteristics of the electricallyconductive multilayer stack, such as the size of the substrate (e.g.,the area) on which the electrically conductive multilayer stack is beingdeposited and the thickness of each of the various layers of theelectrically conductive multilayer stack. For example, the duration ofthe sputtering process will depend upon the size of the target, thepower applied to the target, and because the target can move, the numberof passes that the target makes over the substrate. The substrate canalso move during the deposition process. In consideration of theabove-described variables, the deposition process can be carried out fora period of time sufficient to form the first region, the second region,and/or the third region to an appropriate thickness.

For example, the first region can have a thickness in a range of about0.5 to about 6 nm, such as in a range of about 2 to about 6 nm.Similarly, the third region can have a thickness in a range of about 0.5to about 6 nm, such as in a range of about 2 to about 6 nm. The secondregion can have a thickness in a range of about 3 to about 8 nm.Additionally, a ratio of the thickness of the first region to that ofthe second region can be in a range of about 0.0625:1 to about 1:1, suchas in a range of about 0.25:1 to about 1:1. Similarly, a ratio of thethickness of the third region to that of the second region can be in arange of about 0.0625:1 to about 1:1, such as in a range of about 0.25:1to about 1:1.

As described above, the second region can have a lower oxygenconcentration than that of each of the first region and the thirdregion. For example, as set forth above, the second region can be formedby flowing oxygen at a lower flow rate (i.e., lower relative to theoxygen flow rates for either the first region or the third region)during formation. As a result of the second region having a lower oxygenconcentration than that of each of the first region and the thirdregion, the second region has improved light transmission properties ascompared to the first region and the third region. Consequently, metaloxide layers including first, second and third regions have improvedlight transmission properties as compared to metal oxide layers thatonly include a first region and/or a third region.

Additionally, by having a higher oxygen concentration than the secondregion (e.g., by being formed at a higher oxygen flow rate than that ofthe second layer), each of the first region and the third region hasgreater surface roughness than the second region (e.g., the region oflower oxygen concentration). The increased oxygen concentration, andhence increased surface roughness and increased surface area (or surfaceenergy), of the first region and the third region, relative to thesecond region, improves the adhesion of the metal oxide layer to thesubstrate or other layers (non-limiting examples of which include metallayers, tie layers, base layers, topcoat layers or the like). Forexample, metal oxide layers including first and third regions, withhigher surface roughness than the second region, have improved adhesionto the substrate as compared to metal oxide layers including only asecond region (e.g., a region of relatively lower oxygen concentration).Consequently, the multi-region metal oxide layer described aboveachieves greater adhesion to at least some of the components of thecoated transparency than can be achieved by a metal oxide layer thatonly includes the second region. Thus, the multi-region metal oxidelayer described above has improved adhesion and light transmissionproperties as compared to metal oxide layers that have only a singleregion (i.e., a single oxygen concentration) or that do not vary theoxygen concentration as described here.

In some embodiments, the coated substrate (e.g., coated transparency)provides the functionality required of a modern stealth aircraft canopy.For example, in some embodiments, the electrically conductive multilayerstack 120 has a sheet resistance suitable for radar attenuation. Morespecifically, one or more of the first and second metal oxide layers andthe metal layer can be electrically conductive and have a sheetresistance suitable for radar attenuation. When positioned over atransparency or substrate, such as an aircraft canopy, an electricallyconductive multilayer stack having a sheet resistance suitable for radarattenuation can prevent or reduce the buildup of static charge on thecoated transparency by draining or dissipating the static charge, and itcan provide radar attenuation functionality to the coated transparency.

Additionally, some embodiments of the electrically conductive multilayerstack are transparent and, for example, have a visible lighttransmittance of at least about 61%. In some embodiments, for example,the electrically conductive multilayer stack can have a visible lighttransmittance in a range of about 61% to about 67%. More specifically,the coating one or more of the first and second metal oxide layers ofthe electrically conductive multilayer stack can be transparent and/oranti-reflective. Consequently, a coated transparency or substrate, suchas an aircraft canopy, including a coating made from the coatingcomposition and the electrically conductive multilayer stack can betransparent and, for example, have a visible light transmittance of atleast about 61%. In some embodiments, the visible light transmittance ofthe coated substrate is above 65% (e.g., in a range of about 65% toabout 67%).

In some embodiments, the electrically conductive multilayer stackincludes first and second metal oxide layers including titanium oxide,which, according to embodiments of the present disclosure, has a higherrefractive index than certain other transparent conductive metal oxides,such as indium tin oxide ITO and AZO. As a result of its higherrefractive index, a titanium oxide layer does not need to be made asthick as a corresponding ITO or AZO layer in order to achieve roughlythe same anti-reflective properties. By making the metal oxide layerthinner, the flexibility of the metal oxide layer, as measured by strainelongation, can be improved over other coatings including ITO or AZO, asdescribed in more detail below. Although an AZO layer generally hashigher flexibility than a titanium oxide layer of the same thickness,the metal oxide layers including titanium oxide of embodiments of thepresent disclosure can be ultra-thin and therefore, have a higherflexibility than the thicker AZO layers of previous coatings. As such,an electrically conductive multilayer stack including ultra-thintitanium oxide according to embodiments of the present disclosure can bemore flexible than previous electrically conductive multilayer stacksincluding thicker layers of ITO or AZO. For example, the improvedflexibility of the ultra-thin metal oxide layers including titaniumoxide can improve the overall flexibility of a coating including thoselayers. Additionally, titanium oxide films, such as those included inembodiments of the present disclosure have good light transmittance inthe visible light region (e.g., ˜85%), a high refractive index (e.g.,˜2.1). Titanium oxide also has better environmental stability (e.g.,chemical stability, such as resistance to corrosion induced by water oracid) and mechanical durability than other metal oxides.

Because of the relatively higher refractive index of titanium oxide, atitanium oxide layer can be made thinner than other metal oxide layerssuch as ITO and AZO and still result in an acceptable amount ofdestructive interference in the visible light reflected by the first andsecond metal oxide layers and the metal layer, thereby resulting in anacceptable amount of visible light that is reflected (and consequentlyan acceptable amount of visible light that is transmitted). Although theanti-reflective properties and visible light transmittance ofanti-reflective coatings (such as ITO, AZO and titanium oxide) depend onthe relative refractive index of the anti-reflective coating, thoseproperties also depend on the thickness of the anti-reflective coating.Anti-reflective coatings that have a thickness equal to one quarter ofthe wavelength of visible light (e.g., light having a wavelength ofabout 400 nm to about 750 nm, or about 550 nm), depending upon therefractive index of the metal oxide, produce destructive interference inthe reflected visible light, thereby canceling the reflected visiblelight and increasing the amount of transmitted visible light. That is,when the thickness of the anti-reflective coating is equal to onequarter of the wavelength of the visible light, the visible lightreflected by the anti-reflective coating (i.e., the metal oxide layer)will be out of phase with the visible light reflected by the metallayer, and the visible light reflected from the anti-reflective coatingand the metal layer will be canceled as a result of destructiveinterference. Consequently, the light that would have been reflected bythe anti-reflective coating (i.e., the metal oxide layer) and the metallayer is instead transmitted through the anti-reflective coating and themetal layer. Because ITO has to be made ultra-thin to pass the fourpoint bend test, the thicknesses of previous ITO layers weresubstantially less than one quarter of the wavelength of visible light,thereby limiting the amount of destructive interference produced bythose ITO layers and reducing the amount of visible light transmitted.In contrast to the ultra-thin ITO layers, the presently described firstand second metal oxide layers, which can include titanium oxide, can bemade thinner and still provide acceptable anti-reflective properties.Also, since the titanium oxide layers are made thinner, they are moreflexible and can more easily pass the four point bend test. As such, anelectrically conductive multilayer stack according to embodiments of thepresent disclosure provides suitable anti-reflective properties andvisible light transmittance.

In some embodiments, the first metal oxide layer has a thickness in arange of about 4 to about 20 nm, such as about 5 to about 15 nm, about 8to about 15 nm, or about 10 to about 15 nm. Additionally, in someembodiments, the second metal oxide layer has a thickness in a range ofabout 4 to about 20 nm, such as about 5 to about 15 nm, about 8 to about15 nm, or about 10 to about 15 nm. An electrically conductive multilayerstack according to embodiments of the present disclosure can includemetal oxide layers having the above-described thicknesses and still passthe four point bend test. In contrast, an electrically conductivemultilayer stack including an ITO metal oxide layer would typically needto have an ITO layer having a thickness of greater than 20 nm to havesuitable anti-reflective properties, and would lack the flexibilitynecessary to pass the four point bend test. Because an electricallyconductive multilayer stack including titanium oxide metal oxide layersof embodiments of the present disclosure are more flexible than, forexample, a comparable electrically conductive multilayer stack includingITO metal oxide layers, the electrically conductive stacks ofembodiments of the present disclosure are more flexible, and hence moredurable (i.e., have superior mechanical properties), than certainprevious multilayer stacks.

The present inventors have also discovered that electrically conductivemultilayer stacks according to some embodiments of the presentdisclosure, e.g., electrically conductive multilayer stacks includingmetal layers including gold, exhibit better corrosion resistance anddurability than certain previous coatings. Because gold is lesssusceptible to corrosion than certain other metals, such as silver,electrically conductive multilayer stacks including gold layers are lesssusceptible to corrosion than certain previous coatings (e.g., thoseincluding silver layers). Consequently, electrically conductivemultilayer stacks including gold metal layers are less likely to sufferfrom degradation of electrical (e.g., sheet resistance) and opticalproperties (e.g., visible light transmittance), resulting in improveddurability of coated transparencies including such multilayer stacks.

In some exemplary embodiments, the electrically conductive multilayerstack includes a first metal oxide layer 40 including titanium oxide, ametal layer 50 including gold, and a second metal layer 60 includingtitanium oxide. The first metal oxide layer 40 is positioned over atransparency 10, the metal layer 50 is positioned over the first metaloxide layer 40, and the second metal oxide layer 60 is positioned overthe metal layer 50. For instance, the metal layer can have a thicknessin a range of about 5 to about 20 nm. Additionally, in some embodiments,the metal layer consists essentially of gold. As used herein and in theclaims that follow, the term “consisting essentially of gold” and“consisting essentially of” means that the metal layer primarilycontains gold, but can contain other substances that do not affect thecorrosion resistance, sheet resistance and/or radar attenuationproperties of the gold. For instance, a metal layer consistingessentially of gold would be substantially free, or even completelyfree, of silver (Ag). As used herein, the term “substantially” is usedas a term of approximation and not a term of degree, such that the term“substantially free” means that the material being discussed is presentin the coating composition (or coating), if at all, as an incidentalimpurity. As used herein, the term “completely free” means that thematerial is not present in the coating composition (or coating) at all.

Because gold is less susceptible to corrosion than, for example, silver,a coated transparency including an electrically conductive multilayerstack including a metal layer including gold does not require additionalprotective organic layers, such as a barrier layer, to protect the metallayer from oxidation. For example, a coated transparency according tosome embodiments of the present disclosure includes an electricallyconductive multilayer stack including a first metal oxide layerincluding titanium oxide (e.g., first metal oxide layer 40), a metallayer including gold (e.g., metal layer 50), and a second metal oxidelayer including titanium oxide (e.g., second metal oxide layer 60), withthe proviso that the coated transparency does not include a barrierlayer. As a result, such electrically conductive multilayer stacks canbe less complicated and less costly to produce than certain previousstacks (i.e., because it does not require additional protective organiclayers, such as a barrier layer, to protect the metal layer fromoxidation). By eliminating the barrier layer, the coated transparenciesof some embodiments of the present disclosure can be produced in fewersteps and with fewer materials than certain previous transparencies,thereby reducing cost and increasing efficiency of production.

Nonetheless, some embodiments of the coated transparency of the presentdisclosure can include one or more additional layer(s), such as thoseset forth below. For example, in some embodiments, the coatedtransparency further includes an additional topcoat (e.g., a conductivetop layer including a conductive metal oxide, a quaternary ammoniumsalt, an inherently conductive polymer, and/or other suitable conductiveagent), a base layer(s) (e.g., a layer including a material selectedfrom polyepoxides, polyacrylates, polyurethanes, polysiloxanes, andcombinations thereof), and/or a tie layer(s) (e.g., an acrylic polymerand/or mixture of polymers), such as those described in U.S. PatentApplication Publication No. 2010/0025533 and U.S. Patent ApplicationPublication No. 2010/0028684, the entire contents of which are hereinincorporated by reference.

For example, another embodiment of the present disclosure is shown inFIG. 6. According to this embodiment, a coated substrate 300 includes asubstrate 10 (e.g., a transparency), a polymeric base layer 30, anelectrically conductive multilayer stack 120, and a coating 103including a conductive, anti-static tiecoat 107 and a conductive,anti-static topcoat 105 as described herein. Each of the layers of thecoated transparency can be positioned on or over an adjacent feature (orlayer) in the order shown in FIG. 6. Although not shown, the coatedtransparency can also include an adhesion promoter (e.g., an adhesionpromoter layer), such as 3-aminopropyltriethoxysilane, between thesubstrate and the subsequent layers. The substrate, the electricallyconductive multilayer stack, and the coating (the conductive,anti-static tiecoat and the conductive, anti-static topcoat) aresubstantially the same as those described above with reference to FIGS.1 and 2.

The polymeric base layer 30 can be selected to adhere well to thematerial of the substrate (e.g., polycarbonate and/or polyacrylate). Forexample, the base layer can cover imperfections of the substrate andpromote adhesion of the substrate to another layer, such as the firstmetal oxide layer 40. That is, the base layer 30 couples the substrate10 to the electrically conductive multilayer stack 120, and should becapable of bonding thereto. When used in a windshield, window or canopyof an aircraft, the base layer should not adversely affect the impactresistance of the substrate. Additionally, when the based layer directlycontacts the first metal oxide layer of the electrically conductivestack, the base layer should be hard enough to support the ceramic metaloxide antireflective coating (e.g., the first metal oxide layer).

In some embodiments of the present disclosure, the base layer 30includes a material selected from polyepoxides, polyacrylates,polyurethanes, polysiloxanes, and combinations thereof. A polysiloxanebase layer can be particularly useful as a result of its inorganiccomposition and hardness. As such, the base layer 30 can include apolymeric and/or oligomeric silane, among other species. For example, acoating composition can be prepared from a combination of monomericsilanes and silane terminated polymers that are hydrolyzed in a mixtureof water and acid to form silanols, which are condensed to aprecondensate state after being formed. When the coating composition isapplied to a surface and cured, the precondensate, which includes thesilanols, reacts to form siloxane linkages, thereby forming an exemplarypolysiloxane base layer 30. Alternatively, the base layer 30 can includeany suitable polyepoxide, polyacrylate, or polyurethane. For example,the base layer 30 can include a thermally-curable polyacrylate coatedwith the above-described polysiloxane.

A soft tiecoat (a tie layer) can also be positioned between the baselayer and the substrate. When present, the tie coat dissipates theshrinkage stress that results from the addition of the other layers(e.g., the base layer and the electrically conductive multilayer stack120), and the tie coat accommodates the dimensional change of thesubstrate due to extreme thermal exposure. For example, FIG. 7 shows acoated substrate 400 including a substrate 10 (i.e., a transparency), abase layer 30, an electrically conductive multilayer stack 120, and acoating 103 including a conductive, anti-static tiecoat 107 and aconductive, anti-static topcoat 105, as described above. The coatedtransparency further includes a tie layer 20 between the substrate 10and the base layer 30.

In the case where the substrate is a polyacrylate, polycarbonate, orsimilar organic resin, the tie layer 20 can be an acrylic polymer ormixture of polymers, for example an acrylic polymer made of one or morealkyl acrylates and/or methacrylates. Optionally, the tie layer can alsoinclude one or more additional adhesion promoters, such as additionalmonomers. The layer can be applied to the substrate by gravity coatingor another suitable application technique. In gravity coating, apolymeric solution of the tie layer polymer(s) or precursor monomers isprepared, and the solution is applied to the canopy in the center andalong a longitudinal axis that extends along the entire length of thecanopy. The polymeric solution is then discharged from a nozzle andpoured over the canopy at the top, allowing the solution to flow downboth sides and thereby coat the surface of the canopy. The solution isapplied slowly from one end to another along the longitudinal axis ofthe canopy, until the entire canopy is coated with a tie layer. Thecoating thickness can be controlled by, for example, controlling theviscosity of the polymeric solution. The liquid coating can be appliedby multiple passes to ensure a consistent layer is formed across thecanopy. Any excess drips off the canopy are collected at the bottom,through a gutter, where they can be properly disposed of and/or re-used.

In another embodiment, multiple streams of the polymeric solution aredirected to impinge on the canopy. The solution streams are ejectedthrough one or more nozzles or other outlets at a constant flow rate. Bykeeping the flow rate of the polymeric solution constant, the thicknessof the coating can be controlled. In addition to the flow rate, thethickness of the coating also depends on the viscosity of the polymericsolution. Increasing the viscosity of the polymeric solution increasesthe thickness of the coating. In some embodiments, the viscosity of thepolymeric solution is in a range of about 2 to about 200 centipoise.Once the canopy is coated with the tie layer material(s), it is airdried under atmospheric conditions and ambient temperatures, and thencured using heat or ultraviolet light.

After the tie layer 20 is applied to the substrate 10 and cured, thebase layer 30 is applied by gravity coating or a process similar to thatdescribed above. The substrate, including the tie layer 20 and the baselayer 30, is then allowed to air dry under ambient conditions, and isthen cured.

The first metal oxide layer 40 is applied to the base layer 30 by anysuitable process, such as, for example, sputtering. In one exemplaryembodiment, the first metal oxide layer is formed using a magnetronsputtering process in which a high voltage plasma discharge causes atomsto be ejected from a target, such as a titanium metal or TiO₂ target.The metal or metal oxide then strike the base layer and form a thin,transparent layer of metal oxide. Since the coating is formed on anatomic scale, it is possible to produce uniform layers of films. Fortitanium oxide, the metal oxide layer 40 can be applied at a relativelymoderate temperature, i.e. from about 100° F. to about 200° F. Thesubstrate, including the tie layer 20 and the base layer 30, is heatedto a temperature within that range, and a sufficiently thick layer isdeposited thereon. Additionally, as described above, forming the firstmetal oxide layer or the second metal oxide layer can include varyingthe flow rate of oxygen while sputtering. The target can move during thesputtering process and the target can make multiple passes over thesubstrate.

In an exemplary embodiment, the titanium oxide film is formed usingpulsed DC magnetron sputtering in an argon and O₂ gas mixture at atemperature of about 100 to about 200° F.

Once the first metal oxide layer 40 is applied, the metal layer 50 isapplied using a physical vapor deposition or sputtering process asdescribed above. For gold, the deposition process can be carried out ata temperature of about 100° F. to about 200° F. After the metal layer 50is deposited, the second metal oxide layer 60 is then applied, using aprocess similar to that described above with respect to the first metaloxide layer 40.

After the electrically conductive multilayer stack 120 is formed, theconductive, anti-static tiecoat can be formed thereon. For example, asshown in FIGS. 2, 6 and 7, the conductive, anti-static tiecoat 107 canbe formed directly on the second metal oxide layer 60 to provide aconductive, anti-static tiecoat that is in direct physical contact withthe second metal oxide layer 60.

Alternatively, the coated substrate can include a second tie layer(e.g., a second conductive tie layer) between the electricallyconductive stack and the conductive, anti-static tiecoat, as shown inFIG. 8. According to the embodiment shown in FIG. 8, the coatedtransparency includes a substrate 10 (e.g., a transparency), a tie layer20, a base layer 30, an electrically conductive multilayer stack 120, acoating 103 including a conductive, anti-static tiecoat 107 and aconductive, anti-static topcoat 105, as described above. The coatedtransparency further includes a second tie layer 70 (e.g., a topcoat tielayer) between the conductive, anti-static tiecoat 107 and theelectrically conductive multilayer stack 120. In one embodiment, thesecond tie layer 70 includes a polymeric resin that is compatible withthe conductive, anti-static tiecoat 107 and optionally includes anorganosiloxane compound, which can interact with and bond to the secondmetal oxide layer 60 of the electrically conductive multilayer stack120. The conductive, anti-static topcoat 105 can be made of a durable,weather resistant polymer, such as polyurethane. For example, the secondtie layer 70 can be a tie layer (e.g., an acrylic polymer and/or mixtureof polymers) such as those described in U.S. Patent ApplicationPublication No. 2010/0025533 and U.S. Patent Application Publication No.2010/0028684.

The following examples are presented for illustrative purposes only andare not to be viewed as limiting the scope of the present disclosure.Unless otherwise indicated, all parts and percentages in the followingexamples, as well as throughout the specification, are by weight.

Example 1

A polycarbonate canopy for an F-22A jet aircraft was lightly abraded toincrease its surface roughness and surface area for receiving a primer(3-aminopropyltriethoxy silane, an adhesion promoter). The primer wasgravity coated onto the canopy. Next, a polymeric solution (FX-430,produced by PPG Industries, Inc.,) was applied to the canopy by flowcoating to form a tie layer (tiecoat). The polymeric solution was pouredfrom the top of the canopy and from one end to another, allowing thesolution to flow down and coat the canopy by gravity flow. Excesspolymeric solution was allowed to flow down into a dripping pan and wascollected for proper disposal.

After the entire outer surface of the canopy had been coated, it wascured in a heated oven at about 230° F. for about 5 hours. After thecoating was cured, the canopy was abraded to increase its surface areafor receiving the next coating layer and then cleaned with isopropanol(IPA). A silane basecoat (a silane base layer) was then applied by flowcoating, followed by a layer of a base layer (FX-419, produced by PPGIndustries, Inc.). The coated canopy was then cured in a preheated ovenat a temperature of about 190° F. for about 2 hours. After curing, thecanopy was thoroughly cleaned to remove dust particles and particulatesthat may have accumulated on the surface.

The cleaned canopy was then placed in a vacuum chamber. The pressure inthe vacuum chamber was reduced and the substrate in the chamber washeated to about 100 to about 200° F. Two metal oxide layers and onemetal layer were deposited on the coated canopy at an elevatedtemperature (e.g., about 100 to about 200° F.) using magnetronsputtering. First, a layer of titanium oxide was formed by sputtering aTiO₂ target using a pulsed DC power supply with 300 kHz frequency. Afirst region of the titanium oxide was formed by simultaneously flowingoxygen and inert gas at a ratio of about 1:2 while sputtering for a timeperiod of about 5-10 minutes. A second region of the titanium oxide wasformed by simultaneously flowing oxygen and inert gas at a ratio of 1:29while sputtering for a time period of about 5-10 minutes. A third regionof the titanium oxide was formed by simultaneously flowing oxygen andinert gas at a ratio of about 1:2 while sputtering for a time period of5-10 minutes. During sputtering, both the canopy and the target moved.

Then, a gold layer was deposited onto the canopy at the sametemperature. After the layer of gold was formed, a second layer oftitanium oxide was deposited on top of the gold layer at a temperatureof about 100 to about 200° F. in a manner similar to that describedabove with respect to the first layer of titanium oxide. The canopy wasthen removed from the chamber and carefully cleaned to remove anycontaminants that might have adhered to the surface. A primer layer(acrylate coating with concentration of 1-3%) was formed on the secondlayer of titanium oxide by flow coating. A conductive, anti-statictiecoat was then applied to the second layer of titanium oxide. Examplesof the conductive, anti-static tiecoat were prepared using coatingcompositions including components in amounts in the ranges shown inTable 1. The amounts in Table 1 are shown in wt %, based on the totalweight of the solids of the coating composition. The components listedin Table 1 were also diluted with diacetone alcohol to 65% solids (partsby weight).

TABLE 1 Component Amount (wt %) Capa ™ 4101 10-25 Capa ™ 2101A 2-8Superstat 15-32 TINUVIN ® T-405 1-5 TINUVIN ® T-152 0.5-2  LUMIFLON ®910 LM  5-15 T-12 0.005-0.015 FC-4432 0.1-0.6 N-75 20-50 BAYHYDUR ®401-70 3-9 Total 100

To further enhance the adhesion of the conductive, anti-static tiecoatto the primer layer and the adhesion of a conductive, anti-statictopcoat to the conductive, anti-static tiecoat, 3% (by weight of thetotal solids) of 3-glycidoxy propyl trimethoxysilane (A-187) couplingagent was added to the coating composition prior to the flow coatingapplication of the conductive, anti-static tiecoat (by two componentmixing machine) onto the substrate. The conductive, anti-static tiecoatwas airdried for 2 hours and then cured at 190° F. for 5 hours. Aconductive, anti-static topcoat was formed on the conductive,anti-static tiecoat by flow coating. Examples of the conductive,anti-static topcoat were prepared using coating compositions includingcomponents in amounts in the ranges shown in Table 2. The amounts inTable 2 are shown in wt %, based on the total weight of the solids ofthe coating composition. The components listed in Table 2 were alsodiluted with diacetone alcohol to 65% solids (parts by weight).

TABLE 2 Component Amount (wt %) Capa ™ 4101  5-15 Capa ™ 2101A  2-10Superstat  6-25 TINUVIN ® T-405  2-10 TINUVIN ® T-152 1.0-4  T-4790.1-1  LUMIFLON ® 910 LM 15-45 Capstone 62 AL 0.5-2  T-12 0.005-0.015FC-4432 0.1-0.6 N-75 15-45 BAYHYDUR ® 401-70 2-8 Total 100

Haze and Luminous Transmittance Tests

A 3 inch by 12 inch coupon prepared according to Example 1 was testedaccording to ASTM D1003 using a Haze-Gard Plus instrument. Haze measuresthe clearness and transparency of the film (the film should not betranslucent and diffuse light), while luminous or visible lighttransmittance indicates the amount of visible light transmitted throughthe sample. The coupon according to Example 1 exhibited a visible lighttransmittance of 65.7% and a haze of 1.31%. According to the testresults, the coupon according to Example 1 meets the visible lighttransmittance and haze values required for aircraft canopy, windshieldand windows, which are 58% or above and 10% or below, respectively.

Bayer Abrasion Test

The abrasion resistance of a 2 inch by 2 inch coupon prepared accordingto Example 1 was tested according to ASTM F735 for 300 cycles. Prior tothe Bayer abrasion test, the coupon exhibited a visible lighttransmittance of 68.0% and a haze of 1.60%, as determined by theabove-described haze and luminous transmittance test. After 300 cyclesof the Bayer Abrasion test, the coupon exhibited a visible lighttransmittance of 67.5% and haze of 4.5%, as determined by theabove-described haze test. According to the test results, the visiblelight transmittance and haze of the coupon were not significantlyaltered by the Bayer abrasion test.

Humidity Test

A 3 inch by 12 inch coupon prepared according to Example 1, was exposedto 100% condensing humidity at 122° F. (50° C.). The haze and visiblelight transmittance (VLT) were then measured after 4 weeks, and then 12weeks of exposure. Prior to the humidity test, the coupon exhibited avisible light transmittance of 68.10% and a haze of 0.92%. After 4 weeksof exposure to the 100% condensing humidity at 122° F. (50° C.), thecoupon exhibited a visible light transmittance of 67.00% and a haze of1.26%. After 12 weeks of exposure, the coupon exhibited a visible lighttransmittance of 66.00% and a haze of 1.21%. The crosshatch adhesion (asmeasured using 10 tape-pulls) of the coupon after both 4 and 12 weeks ofexposure was 100% with excellent cosmetics.

Humidity and Solar Radiation (QUV) Test

A 3 inch by 12 inch coupon prepared according to Example 1, was exposedto cycles of 8 hours of ultraviolet (UV) radiation at 140° F. (60° C.)at 0.49 W/m² followed by exposure to condensation for 4 hours at 122° F.(50° C.). The haze and visible light transmittance (VLT) were thenmeasured after the cycles had been repeated for a total of 4 weeks, andthen 12 weeks. Prior to the humidity and solar radiation (QUV) test, thecoupon exhibited a visible light transmittance of 65.00% and a haze of1.68%. After 4 weeks of cycles the coupon exhibited a visible lighttransmittance of 64.5% and a haze of 2.00%. After 12 weeks of exposure,the coupon exhibited a visible light transmittance of 64.1% and a hazeof 2.5%. The crosshatch adhesion (as measured using 10 tape-pulls) ofthe coupon after both 4 and 12 weeks of exposure was 100% with excellentcosmetics.

Rain Erosion Test

A 1 inch by 1 inch coupon prepared according to Example 1 was exposed tosimulated rainfall at a speed of 550 miles per hour (mph) at theUniversity of Dayton Research Institute (UDRI). The coupons wereinspected for degradation of the coating after 1 minute, 11 minutes and22 minutes of exposure to the simulated rainfall. No damage to thecoupon or loss of adhesion was observed after 1, 11, and 22 minutes ofexposure.

Solvent/Chemical Exposure Test

Several coupons were prepared according to Example 1. A pool having adiameter of 2.5 inches was created on the coating surface of each couponusing tacky tape. The pools respectively included water, a 50/50 (w/w)isopropanol/water mixture, substantially pure isopropanol, a mild soapsolution, naphtha, Kilfrost, JP-5 jet fuel, and JP-8 jet fuel. Thecoupons were continuously exposed to the respective solvents/chemicalsfor a period of 10 days (and the solvents and/or chemicals werereplenished as necessary). After 10 days, the coupons were inspected forfisheye, delamination, or distortion of the surface. The coupons werealso tested for crosshatch adhesion in the areas of exposure. No changesto the coupons were observed and the crosshatch adhesion was 100%.Additionally, the light transmittance and haze of the coupons weremeasured before and after the chemical/solvent exposure test, and nosignificant change in the light transmittance or haze was observed.

Although various embodiments of the invention have been described,additional modifications and variations will be apparent to thoseskilled in the art. For example, the coated substrate can haveadditional tie layers or primers, conductive tie layers, alternatethicknesses, additional components, etc. As used herein, the terms “tielayer” and “base layer” may be considered synonymous with the terms“tiecoat” and “basecoat,” respectively. Also, as the individual layersincluded in the coated substrate are formed, they can be cleaned beforethe next adjacent layer is deposited. For example, the first tiecoat canbe cleaned with a solution such as a mixture of water and alcohols, andthen dried to remove any surface water, which could interfere with theflow properties of the polysiloxane of the base layer 30. The inventionis not limited to the embodiments specifically disclosed, and the coatedtransparency, its layers, and compositions may be modified withoutdeparting from the invention, which is limited only by the appendedclaims and equivalents thereof. Throughout the text and claims, the word“about” is used as a term of approximation, not as a term of degree, andreflects the penumbra of variation associated with measurement,significant figures, and interchangeability, all as understood by aperson having ordinary skill in the art to which this inventionpertains. Additionally, throughout this disclosure and the accompanyingclaims, it is understood that even those ranges that may not use theterm “about” to describe the high and low values are also implicitlymodified by that term, unless otherwise specified.

What is claimed is:
 1. A coated substrate comprising: a substrate; anelectrically conductive multilayer stack on the substrate; and a coatingon the electrically conductive multilayer stack, a thickness of thecoating being 5 to 10 mils and the coating comprising: a conductive,anti-static tiecoat on the electrically conductive multilayer stack; anda conductive, anti-static topcoat on the conductive, anti-statictiecoat, and the conductive, anti-static tiecoat being formed from acoating composition comprising a hydrophobic first aliphaticpolyisocyanate, a second aliphatic polyisocyanate comprising ahydrophilic portion, a polyester polyol, a hydrophilic polyol, and afluorinated polyol.
 2. The coated substrate of claim 1, wherein athickness of each of the conductive, anti-static topcoat and theconductive, anti-static tiecoat is 2.5 to 5 mils.
 3. The coatedsubstrate of claim 1, wherein the thickness of the coating is 5 to 8mils.
 4. The coated substrate of claim 3, wherein a thickness of each ofthe conductive, anti-static topcoat and the conductive, anti-statictiecoat is 2.5 to 4 mils.
 5. The coated substrate of claim 1, whereinthe thickness of the coating is 6 to 8 mils.
 6. The coated substrate ofclaim 5, wherein a thickness of each of the conductive, anti-statictopcoat and the conductive, anti-static tiecoat is 3 to 4 mils.
 7. Thecoated substrate of claim 1, wherein a thickness of the conductive,anti-static tiecoat is at least 3 mils.
 8. The coated substrate of claim1, wherein a thickness of the conductive, anti-static topcoat is atleast 3 mils.
 9. The coated substrate of claim 1, wherein theconductive, anti-static tiecoat is substantially free of inherentlyconductive polymers, ionic liquids, conductive oxides and carbonnanotubes.
 10. The coated substrate of claim 1, wherein the conductive,anti-static topcoat is substantially free of inherently conductivepolymers, ionic liquids, conductive oxides and carbon nanotubes.
 11. Thecoated substrate of claim 1, further comprising a tiecoat between thesubstrate and the electrically conductive multilayer stack.
 12. Thecoated substrate of claim 11, further comprising a basecoat between thetiecoat and the electrically conductive multilayer stack.
 13. The coatedsubstrate of claim 1, further comprising a primer layer between theelectrically conductive multilayer stack and the conductive, anti-statictiecoat.
 14. The coated substrate of claim 1, wherein the coating has aresilience such that the coating can be stretched to a length 50% ormore longer than the as-formed length of the coating substantiallywithout tearing the coating.
 15. The coated substrate of claim 1,wherein the coating has a resilience such that the coating can bestretched to a length 100% or more longer than the as-formed length ofthe coating substantially without tearing the coating.
 16. The coatedsubstrate of claim 1, wherein the coating has a resilience such that thecoating can be stretched to a length 200% or more longer than theas-formed length of the coating substantially without tearing thecoating.
 17. The coated substrate of claim 1, wherein the secondaliphatic polyisocyanate further comprises a hydrophobic portion. 18.The coated substrate of claim 17, wherein the hydrophobic portion of thesecond aliphatic polyisocyanate comprises an isophorone diisocyanatemoiety or a derivative thereof.
 19. The coated substrate of claim 1,wherein the hydrophilic portion of the second aliphatic polyisocyanatecomprises a polyether chain.
 20. The coated substrate of claim 1,wherein the second aliphatic polyisocyanate comprises a polyether chainbonded to an isophorone diisocyanate trimer.